What I'm giving here is very general advice, available from pretty much everywhere. But if you do follow any of this, do it on paper first. Also DYOR, natch.
My strategy would be to only sell if it was higher than when I bought it, even if that took a long time.
That's pretty much the
exact opposite of what you should do. It's a cliché, but true for general trading: cut your losses short and let your profits run.
Imagine there was a market where 3-out-of-4 of shares would drop in value by 50%, and only 1-out-of-4 would go up by 50%. You'd get wiped out, right? But the beauty of trading is that YOU get to decide what you do. So if (in that market) you cut your losses to 10% per share, and let your winners run to the top, you'd come out ahead.
You should EXPECT at least as many losers as winners - but THAT DOESN'T MATTER. You can still make money despite more losers than winners by playing smart and cutting those losing trades off. Don't hold on to them!
Money management will make you money. In fact, IMO that's where most of the money is in this stuff. There's a lot of finesse to learn that can make your win rate better or make your winners bigger or cut your losses even further, but all of that is just a bonus. Learn money management, and honestly, random share selection could well do the rest for you.
Really simple system? Say you have $25k. Split it into 20% batches: $5k each. Buy 5 different batches of shares for $5k each. Pick them from the top200 and just pick stuff that seems to be going up (don't try to pick the bottom of a falling share - just pick stuff on a good up-trend).
Set your stop loss (aka a conditional order -> falling sell) at 10% less than your buy price. That will limit your loss to $500 on any one trade, which is 2% of your money. Some will fall out the bottom, but you'll only lose $500, and you can get back in on an up-trending share. Come back every month or so and raise your stop losses if the prices have gone up - maybe give 15% for a share you like, to give it room. That's how you'll sell shares - as they fall from their highs. NEVER lower a stop loss. They stay where they are or they go up. NEVER down (well ok, there's an exception for ex-div - I'll mention that at the end).
So the
system sells all your shares. The ones that fall will lose no more than $500 (barring disastrous gapping). The ones that go up can make a lot more than $500, and that's how you make money.
Get a broker (BellDirect is a good starter one, IMO - cheaper than most, free conditionals, good layout, etc). that will send you an email when a share sells (most do). Then you don't have to worry about it until you get an email to tell you that something sold, and then you just have to jump on, find a new share to buy (ie one that's going up) and buy it. Set your stop losses, done. Jump on every month or two to bring stop losses up if things are going up. Easy.
Refinements: you might want to pick shares with decent dividends, though still trending up of course. Dividends are good for long-termers. You might want to sign up for a newsletter or something to help you sift through the dross when it comes to buying time. You might want to learn some basic technical analysis to help you better pick when to get into a stock, and how to get better at seeing when a share is falling again. You might want to get shares from unrelated sectors, so you don't get all 5 dropping at once for the same reason (eg don't buy 5 gold miners, since if gold drops then, instead of a $500 loss for one stock, you'll get all 5 drop out, making it a $2500 loss). And if you see that a share wobbles about so much that your 10% stop loss is likely to get hit the day after you buy it, perhaps look for something else.
But in general, that's all a lot more work for not necessarily much more return (unless you're willing to get serious). The "simple" advice of picking stock that's going up is something that might need a bit of research, but you can generally eye-ball it on a chart - just make sure you're looking at an up trend a good couple of months long. Weekly trends don't count.
So there y'are. Buy stuff wots going up. Sell stuff wots going down. Do that on paper and see how you go.
(Oh, the dividend thing: after eligibility for the dividend passes (ie the share goes "ex-dividend") you can expect the price to drop a fair bit. This is the one case where you might be justified in putting your stop loss down, and then only by the amount of the drop on the day after the ex-div (so if your stop was 15 cents behind the price, and the dividend went ex for 10 cents, the price may drop about 12 cents the next day. That'd make your stop only 3 cents behind the price. In that case, it would be ok to put your stop loss back down to 15 cents).