how to choose a price for buying

You are looking at a 10 year chart. The stock has gone up and down a couple of times, in fairly big waves, during that time. There's an earlier very distinct bottom. Now, prices are approaching that low again. Actually, let's say prices now are twice that low. That's an interesting place to buy, because you can buy here, and then, if it goes down further, you can buy again at half your first price, which means you can double your holdings for only 50% more, or triple your holdings while only doubling your investment.

But, just because the stock is down doesn't mean it's making a bottom. You should probably only buy here if there's a definite signal. Remember, that lower bottom is like a powerful magnet, pulling prices down towards itself. Even if a bottom is signaled, there's a chance prices will go lower, even to the old low.

But there could be signals that are compelling, in a market like this. Chief among them would be a spiky low. Basically, I'm placing orders at major bottoms, and and spiky lows, and, if a stock has returned to the area of a major bottom, and makes a spiky low, I place an order at the spiky low.

Orders placed at spiky lows aren't guaranteed to be filled. Prices are very likely to dip back towards the low, but might rally before making it all the way there. If they are going to do that, they will usually give a signal. One such signal could be another, smaller spiky low near the earlier one. Move your price up to that one. Another would be a period of narrow sideways motion - describing almost the point of a needle, near your spike low in price, pointed towards the future. In that case, place your order at the market price - at the point of the needle - but use a LIMIT order. Prices could jump any time. (You don't want to jump with them, by using a market order.)

Spiky lows can be really crazy looking. You'll think they're some kind of mistake. I think those are very significant. They can also be quite tiny. A tiny but very distinct spiky low near other low price indicators could be a good buying opportunity.

You can sometimes order at spike lows from the past. There are also stocks that have dropped substantially, say by 75%, at some time in the past, and then tracked sideways near the new low price area for several years. Though this is not a guarantee the price will go up, if the overall chart speaks to you - narrow sideways action for an extended period at a low price, and looking strong somehow - ... well, I'm placing that kind of order.