When you are writing your post... below the box you are typing in is a list of options which you can check or uncheck...and each person can do that for their own interactions with the site...
Put a check into " email notifications" and when someone replies to your thread you will get an email...
Also go and look at the 'user cp'.. this will allow you options also..
And play with the search feature... it is very helpful.... after you have read what has already been said about a subject then you can ask a good question for whatever is not clear...