Beginner poker players often have a tendency to play bad poker hands, either from a lack of knowledge, or too much practice on play money poker tables (where anything goes). If you intend to make money playing poker, or at least not lose it, you need to create standards of play. Learn to avoid playing poker hands which are bad, and your bankroll will go a lot further. Lee Jones, in his book "Winning Low Limit Holdem", identifies several hands which should be avoided at all costs:

The Dominated Hand - this refers to playing a high card (K, Q, J, T) with a very low kicker. If you flop top pair, and anyone calls your bet, there is an excellent likelihood that you are out-kicked. The only time you might consider playing this type of poker hand, is if the cards are suited. However, in this case you are only hoping to flop your flush. Otherwise, give the hand up.
Two or Three Gap Connectors - two gap connectors are cards which require two cards between them to make a straight (for example 8-5). Three gap connectors require three cards (example 10-6). The problem with these cards is that the only hand you can make is a straight, and there is only one possible way. For example, if you played 10-6, you need to hit 7, 8, 9 to get your straight. If these cards do fall, you don't even have the nuts, as the player with 10-J has a higher straight.
Small Pairs - small pairs should not be played out of position, or in cases where the pot odds are not appropriate. You are only a very slight favorite to any overcards.
Suited Qx, Jx - many amateurs make the mistake of assuming that any queen or jack suited is a playable poker hand. In the long run, these cards will cost you a lot of your bankroll.
Any Two Suited - time and again players call with any two suited cards. This is very dangerous. If a flush is dealt, it is very likely that you will be beaten by a higher flush. If a flush draw is dealt, you can spend a lot of money chasing the flush, and either not get it, or be taken down by the higher flush.