Many players spend a great deal of time memorizing long opening openings for their chess game. Memorizing openings, especially for the more inexperienced player is generally a waste of time. It is good to see what the opening options are, but sticking with the same opening and ignoring the play on the board is a mistake. The inexperienced players often do not apply basic opening principles, like consistently getting all their pieces involved in the game before starting a battle. Ironically, these same players also often repeat the same general opening mistakes even though these opening mistakes should be relatively easy to identify and avoid.
No matter how many specific chess openings you learn, you should always consider general opening principles. For example, many players start middle game activities without their rooks, and do so game after game, year after year, ignoring "Move every piece once before you move any piece twice, unless there is a tactic", or the opening concept of "Keep your entire army active at all times." Others will delay castling until it is too late, create needless weak squares, or do not use break moves to give pieces early middle game mobility. If you follow proper chess principles you will be surprised how well you can play without knowing all the latest theories of chess.
After each game, or set of games, look up every opening you play and ask yourself "If someone played the same moves again, where would I differ?" This results in you gaining dramatic insight into how you can rapidly improve your game. It has been said, in a variety of forms that repeating the same mistake over and over and expecting different results is insanity. Try not to repeat the same tactical mistakes in your games and expect to improve.