1. Develop strong starting hand requirements. Choose what hands you play and stick to them as best as possible. A tight player should only play mid-to-high pocket pairs, high fitted connectors and high fitted face cards. Loose players can play more hands but without reckless play is your playing style (which in my experience is not very profitable) you need to buckle down on your starting hands.
2. Take into account your position at the table relative to the dealer and the blinds. If you act within the first two to three positions after the big blind than you should play your tightest game here. Play the lowest number of hands in this area of the table because you will be out of the position the rest of the hand and will have to act with minimal information about your other opponents. Once you enter middle positon which are the two to three spots after first position you can loosen up a little bit but still keep it fairly tight. Once you reach late position which is the button and the one or two spots to the right of the button, you can play your loosest game here to take advantage of your position. In the blinds I suggest playing similar hand requirements as late position but if it folds around and only the dealer calls or its just you and the big blind fold only the worst of hands.
3. When you make a raise pre-flop do not ever raise based on the strength of your hands (ex. Raising 5x the blind with aces but 2-3x with 10s). Your investments should be based on table position and the amount of players in the pot. If its a family pot, it is going to take a larger raise to drive them out due to being offered pot odds. In earlier position you can safely raise less and as you get to later position your plans can get to the 5x the big blind range. I would not suggest going higher than 5x the big blind without its multiway and you have a monster that you do not want a lot of players against. Remember, you do not want aces or kings in a multiway pot, try to get it down to at most 2-3 players.
4. After making a pre-flop raise, if the action checks to you it is wise to make a bet around 1/2 the pot (make sure to vary it just to keep competitors guessing) whether or not your hand hits that way your opponents can not think "He checks when he misses and only bets when he hits." This strategy is called making a continuation bet. For example, you have AK the flop comes 2-5-9 you make a bet. Make a similar sized bet even with a flop of A-2-7. That way opponents will not know when you have it and you are more likely to get paid.
5. When you flop a monster hand like trips, straight or flush its often a profitable strategy to check it to your opponents and let them bet then smooth call when action comes back to you. Repeat this on the turn and then if you think your monster held up you can either bet if you think your opponent will check the river or check it one more time then put in a value raise over the top to try to get a little bit more out of it. This strategy is known as slow playing or trapping. Be cautious though, if you flop trips or a straight and theres better draws on the board like two hearts or even three hearts than you may want to speed up and price opponents out from getting a cheap card to make their flush.
6. When you think or know you're beat then fold. Unless you're being offered ridiculous pot odds to call than just discriminate yourself and make the fold. Great players learn to lay down great hands. If you have trouble knowing when you're beat than sometimes you should play a very tight game until you improve so that way you are ahead of opponents most of the time.
7. Do NOT ever give a free cards when you make a hand on the flop. The only exception is if it is a very safe flop for a monster hand that is illegally to be beat on later streets. You do not want to give a free card that beats you when a bet may have gotten them off the draw.