That's kind of why I've stayed away from it until now, but I've come to the conclusion that weight training is what's missing from my fitness routine, so I'm going back to it. (And hey, I've missed doing it.)
I decided rather than trying to come up with my own routine (since I don't trust myself for a lot of reasons) I'd look for one online. I found this three-day program for dumbbell-only lifting so I'm going to try that out. I've always preferred free weights (dumbbells and bars with plates) versus machines, plus I've got dumbbells at home and just needed a flat bench, so then I could work out at home. I have much better success with home workouts than going to a gym.
(Cat not included.)
The above setup cost me about $300. I ended up getting the stacked weights instead of individual dumbbells because they save space. This brand had reasonable reviews (I've heard a lot of bad stuff about the Bowflex variety) so we'll see how they work out. I'd say if you don't want to spend the money to buy things new, just scope Craigslist in a couple of months once the New Year's resolutions start dropping like flies. (Also, if you're in Colorado and come get them, I'm getting rid of my old dumbbell set, which goes from 5-12 lbs. Just light weights, sorry.)
So in honor of getting started for the new year, here are some basics for weightlifting:
Good technique is everything. The site I linked to has videos for each exercise, which is excellent. Proper technique in execution will (a) help build muscle better and (b) keep you from hurting yourself while you're doing it. I cannot emphasize this enough.
Don't overtrain. Don't just randomly add extra exercises to your routine. Find a good one that works everything over a week and don't hammer on one muscle group more than that. Are you listening, self?
Rest. Resting your muscles is as important as lifting. You need to give them time to heal before working them again or you'll just hurt yourself. That's why, for example, I'm only doing three days a week, with a day off between.
Go to the brink of failure. This means picking a high enough weight that you'll have to work, and aim to feel like you can't possibly lift it one more time at the end of your set. You don't want to actually get to the point where you drop the weights, though, since you can really hurt yourself doing that.
By the way, cats apparently love weight benches. Trying to get the little bastards off of it so I can do bench press is a feat of strength all its own.