If you're just starting out collecting and painting miniatures, you don't want to be the guy with hundreds or even thousands of miniatures sitting around, unpainted. This is one of the greatest pitfalls in the hobby. Miniatures are meant to be assembled, painted, seen, and gamed with, not to sit languishing in a box someplace, unpainted, unappreciated.
I have just under 1800 miniatures. About 300 are the pre-painted plastic miniatures that WotC put out during the heady days of 3e/3.5e. The rest are either plastic or metal, used for D&D/RPGs, Hundred Years' War historical battles, or Warhammer Fantasy. All are 28mm. I hate to admit it, but at least three hundred of those are not painted. Sometimes I get dismayed at the prospect of painted them all. I've sold some already--but, for some reason, people keep giving me more. I also used to pick up miniatures when they'd go on sale.
You think that's a lot of miniatures? Not from what I've seen and heard. I know a guy whose entire basement is filled with boxes and boxes of miniatures. Most of them, however, are painted. I also heard of a story where an old wargamer died, leaving at least 10 thousand miniatures behind--the vast majority unpainted, stored in his basement, for his wife to divvy out to his friends or sell on ebay. They kept going through his basement finding more. He just kept buying more and more miniatures, in different scales for different games.
I bought most of my miniature because I thought, that someday, I'd run a gigantic siege at the end of my Last Campaign. It didn't happen. I was nowhere near close to painting all of those miniatures and terrain for the scenario I had in mind. That campaign is over, now what do I do?
Back when I first starting buying and painting miniatures for D&D and wargames, I wish somebody had given me the following advice. Actually, a friend did give me some of this advice, but I was young and thought I had all of the time in the world to pursue many projects at once. Now I'm much older and have a bunch of miniatures to paint, some of which I bought over a dozen years ago. This advice is geared toward the beginner. Still, even a veteran can get some use of this information--I was a veteran when I realized that I should have listened to my friend back in the year 2000.
1. Start a project and finish it before moving on to another. This is the advice my friend gave me. I should have heeded him. This applies to painting up armies for historical games or warhammer, or even figures for roleplaying games. Basically, buy only what you know you can paint in the foreseeable future. Finish that before moving on.
If you invest in an army, finish it within six months to a year. Get it done. If you purchase a single figure for roleplaying games, finish it within a month, if not a week.
Having a bunch of unpainted miniatures laying around can be overwhelming and can harm the sense of accomplishment you get when you do finish painting a figure or an army unit.
2. Start small. Here's dirty little secret: painting miniatures is the hobby; gaming is just an excuse to show off the miniatures. It took me awhile to figure that out. A lot of players focus on the rule system. They'll study the rules like a textbook--even more so, perhaps. The rules are important, but...
You will spend far more time painting miniatures than gaming with them, especially with wargaming. Thus, you need to make sure you enjoy the primary aspect of the hobby.
Thus, start by painting only a few miniatures, a unit at most if you're getting into wargaming. It is better to figure out if you like painting miniatures when you've only invested in $50-60 or so, rather than after you've spent hundreds of dollars. $50-60 is about average for the price of entry--at least with 28mm figures, considering the cost of the miniatures themselves, brushes, paints, bases, sealants, etc. This is an expensive hobby, make sure you like it.
3. Playing a Few Games Before Making the Big Leap. Most gamers are willing to let you share their miniatures to prospective players during a game. In roleplaying games like D&D this shouldn't be a problem. Most wargamers I've encountered will let you have a command to push around. It just depends on how many people are playing in a given game and if there's enough miniatures for every body.
Many gaming stores are a great place to meet fellow gamers (I say "many" because some are not).
That's the top three. There's more advice that applies to specific games and genres. Warhammer, of course, has its own peculiarities and pitfalls. In upcoming Mini Mondays I'll probably go into what those are.
As for painting advice, there's plenty of information out there that I won't go into here.
In summary: "Make sure you're having fun while painting your miniatures done."
(Yeah, I'm not sure if that's grammatically correct, but it works.)