The more closely you examine your decision making processes, the better able you will be to improve them.
One great way is to record your thoughts, predictions and rationale, and later revisit them to see if and why you were wrong, so that you won't make the same mistake twice.
You may want to consider the elements below when you're thinking about buying or selling.
It helps clarify the decision, it helps with record keeping and it helps with learning.
You may want to change them to suit your own needs, or come up with totally different ones.
Remember that these elements are not intended to be comprehensive, they are just to give you ideas.
You may also want to analyze other aspects of the company.
Also periodically check the transactions you decided not to do, to see if you made the right choice and why.
Does this investment fit into your overall strategy?
Does this purchase make sense given the rest of your portfolio?
What is this stock worth?
What is the stock's price?
What is the downside risk of this investment?
What could go wrong?
What is the upside potential?
What news, events or trends should you watch for that might affect the stock's price, how likely are they, and what would the effect be?
When will you sell this investment?
Will it be sold after a certain period of time?
Will it be sold when you reach a certain profit level?
Why that amount?
What percentage of your portfolio does this represent?
Once you've completed the Analysis above, if you decided to go ahead with the transaction, you will probably want to record the following information:
Company name and symbol
Date shares bought
Plan of when/why to sell
Under what cirumstances would you buy again?
Periodically, you should examine the forms you've filled out to see how well you did. Put them in order, from best to worst, and see if you can discover any patterns.
Maybe your circle of competence is different than you thought; or maybe you'll find that you hold too long or not long enough.