I learnt many years ago the hard way too and I would like to let you know, what I learnt:
be careful and watch, watch, watch and don't put all your money in one basket.
don't look back when you sold to early and its going higher - don't be greedy, there is always another stock you can buy cheap with the money you made.
learn to cut losses and don't throw good money after bad to lower average. do that only if you are convinced you have a good one and it came down for some reason which did not change the fundamentals ofthe company.
don't chase a stock. buy cheap - sell high, but without greed.
develop a feeling (your intitution) when you read about the stock, looking at the chart, reading posts and looking who is posting on the board and of course the companies homepage... the best advice is your inner voice. .at least that is working very well for me.
I wish you all the best
