Self Improvement - Broad vs Focused

Splitting these into things that are time investments and things that you want to stop doing is one way to look at it. Another way to look at it is to divide things into recurring and non-recurring time investments. For example, exercising regularly is a recurring time investment, that takes a few hours every week; but scouting out gyms, choosing an exercise routine and setting the precedent for doing it is a one-time investment. For things that look like recurring time investments, or that look daunting, try to split off one-shot tasks that move you in the right direction.

Spending a higher percentage of the time working at a computer actually getting stuff done, instead of getting distracted by the internet.

More concretely: Install Leechblock (or a similar plugin) to either give yourself a time limit, or limit which times of the day you can surf in. Make your blogreading more efficient with RSS feeds. Choose the site with the lowest intellectual content to addictiveness ratio and delete it from your bookmarks.

finding some recurring activity where I'll probably meet the same people over and over to improve the odds of making longterm friends.

More concretely: Browse meetup.com and similar sites for recurring activities in your area which others have organized.

Improving my diet, which mostly means eating less cheese. I really like cheese, so this is difficult.

It is much easier to change your diet by adding things than by removing things. To displace cheese, add other sources of fat and protein. However, removing cheese from your diet would not necessarily be an improvement, and it's unlikely to be the best available improvement.

Stop making so many off-color jokes. Somewhere there is a line between doing it ironically and actually contributing to overall weight of prejudice, and I think I've crossed that line.

More concretely: come up with some general-purpose jokes that aren't off-color, and start using those instead.

Somehow stop losing things so much, and/or being generally careless/clumsy. I lost my wallet and dropped my lap top in the space of a month, and manage to lose a wide array of smaller things on a regular basis. It ends up costing me a lot of money.

More concretely: cultivate the habit of checking your inventory whenever you exit a building (even if you really do have everything). Put some thought into how you manage the inventory items you tend to carry. Throw out any clothes with insufficient pockets.

I support the idea of deciding on places to keep things. I have several small objects I need to keep with me (wallet, phone, iPod, appointment book) and I avoid losing them by always putting them in the same pockets. This also works for some members of my family who have your same problem.

Regarding cheese: how do you normally consume it? Finding healthier alternatives that occupy similar niches might help. For instance, if you usually spread it on bread, you could substitute hummus; if you're making paneer-based curry regularly, you could substitute tofu; if you're melting it on top of nachos, I have no suggestions, because nothing melts quite like cheese.

I'm just curious - a few people have apparently voted this down. Why is that exactly? If I'm breaching some etiquette I'd like to have it explained to me.

The cheese, losing things, and new apartment goals seem like they can be solved in whole or part by one-time changes. Alicorn's suggestion about cheese sounds right, and you should also consider switching to healthier cheeses and avoiding or altering situations where you would snack on cheese. Similarly for losing things, I found that I would lose stuff less often once I had dedicated locations for key items (e.g. keeping my wallet by the door, my cell phone in my jacket pocket), which is also a one-time decision followed by a commitment to sustain the practice.

But you might want to wait on physically organizing your stuff until you get the new place. It seems like the move would unlock a lot of extra time you could use to work on all the other goals. You just have to remember to keep up your momentum once you make the move; for me, there's always the temptation to give myself a pat on the back and permission to relax for a while after doing something big.

Basically, I'd suggest starting with the improvements that are just about removing obstacles, impediments or distractions (for these, you just need a one-time burst of energy, which even many ordinarily akrasic people can do, I think), then use your extra time & energy to tackle the ones that are about altering existing habits or creating new ones.

What sometimes helps me retain my momentum, after a big improvement like a move, is making sure my internal narrative notices that if I'm not working on something now, when I have momentum and a newfound supply of extra time, then I'm not likely to do so in the future; in other words, the way I spend my time now is not being traded with future time, but is instead representative of future behavior. So in this sense when I start now on one thing, I am inclining my future self to start on the next task.

Consider introducing a new, harmless source of short-term gratification to your lifestyle, and only using it to reinforce behavior consistent with these goals.

On #1 you may consider adopting a standing desk. Standing while working improves your posture and also is a form of mild exercise.

I'm a firm believer in working on one thing at a time when it comes to improving skills, and defining "thing" as narrowly as possible.

In animal training, the advice is usually to work on one aspect of a behavior at a time. For example, if I'm training my dog to sit, I decide ahead of time whether I'm working on latency (how quickly does she sit when I cue her?), duration (how long will she hold a sit before I release her?), form (where does she put her feet?), etc. A training session will make some progress in that area that generally carries forward, and then I can switch areas.

Humans aren't dogs, of course, but I suspect there's a shared principle.

(Unrelatedly: I used to be a cheesehound and then cut cheese out of my diet almost completely about three years ago. But I did so by having a stroke and being post-traumatically hypervigilant about food for about a year. I don't recommend that strategy.)

I agree with other commenters that suggest getting a new place be your top priority.

You could try geting somewhere close enough to work that you can jog (or cycle) there and back each day. That should get you your exercise and appreciate-the-outdoors-warm-fuzzies, as well as saving you the cost of a gym membership.

As to your goal to get more exercise:

I work at a computer for 9 hours a day, and spend about 3 hours commuting on a train

I wouldn't spend extra energy working out. When I commuted last summer 3 hours/day I found that working out wasn't worthwhile. I exercised like a maniac the first month and a half and then just lost all motivation. Maybe 30 minutes, 3 times per week, but in order to keep a healthy body, I would suggest improving your diet. This is just advice; take it or leave it, I'm not trying to tell you how to live your life.

1. No bleached white flour, no hydrogenated oils. No amount of these is acceptable in a healthy diet. Sources: any fast food. Most breaded/fried food at restaurants. Margarine (I think). Check the ingredients of anything you eat. Anything that says partially hydrogenated, or most white doughs you should avoid.
2. Minimize sugars and saturated fats. These aren't unacceptable in any amount, like bleached flour and hydrogenated oil. However, they should be kept to an absolute minimum (and you can actually really cut them out completely, it's not impossible). Sources: non-lean meats, desserts, candies, many many other things (check nutrition facts!). For every gram of saturated fat you consume, try to consume a few grams of polyunsaturated or monounsaturated fats. These are found in nuts and grains.
3. Check where your calories are coming from. If you're trying to lose weight, get around 40-50% of your calories from protein, 40-50% from carbs, and <20% from fats. If you're happy with where you are, 30-40% protein, 50-60% carbs, 10-20% fats. This will change depending on whether you're male or female, and whether you are prone to being overweight, and many other factors, such as your activity level, any health problems you may or may not have, etc. FYI, 4 calories/gram each of protein, carbs, 9 calories/gram of fat. Minimize the amount of simple carbs you consume (e.g., sugars, I even try to stay away from potatoes, but they aren't terrible) and maximize the amount of complex carbs you consume (grains and rice are great, bread made from good flour is a good source of grains)
4. Make sure any changes in your diet are sustainable. If you aren't able to make your diet completely healthy, only change it as much as you can stand to live with. Your diet should be a lifestyle, not a 3-6 month fad. If you change your diet for a year or more, you may find that being healthy is a motivating factor for you, and you may be encouraged to keep improving it.

Good luck, and if you can find it in you to work out as well, you're far more motivated than I am.

Edit: after reading the rest of your post, I see that you want to move closer to your job. I strongly suggest this, especially if you want to have a social life and work out. With 12 hours/day spent on your job, having both of those is going to be really tough. Also, I saw that improving your diet is important to you. I do suggest cutting down on cheese. When I did a calorie count for my diet I had to do this as well, and it really made me sad...but it's worth it, in the end. However, this depends on what else is in your diet. If you don't have many sources of fat in your diet other than cheese, you may be okay, but this is not likely, fat is everywhere.
remember, immediate gratification<good diet

Are you intentially trying to take advantage of the New Year's timing for your resolutions?