Preflop

Make sure to raise with top-pairs and top-connectors to drive out low-pairs and various connectors and to build the pot in case you hit.
Be selective with your starting hands. Dont call too many hands, see starting hands
Be aware of your tableposition
Have respect for strong tight players

Flop

The Flop is probably the most important moment in Texas Holdem. Your ability to read the flop will be a huge factor in your success in Texas Holdem.

The folloing facts is important how to valuate the flop:

• The strength of the hand
• Type of flop
• The number of opponents
• The opponents possible hands
• Size of the pot

  Always value the relative strength of your hand compared to the flop and your opponents possible hands before you decide your betting strategies

  If you have an overpair, bet or raise to eliminate your opponents and to protect your hand.
  If you flop toppair you should play it aggressively, be aware of your kicker.Top pair is strong after the flop, but definitely not strong enough to sit on and slow play.
  
  When you flop a draw, use pot odds to determine calling.
  
  If you flop a good monsterhand when board isn´t dangerous you should slowplay to increase the pot. Wait till the more expensive turn and river to begin extracting chips from your opponents.
  
  If the flop is no help for you, check and fold to any bets. Taking bad hands to the river will take a major toll on your bankroll.

Turn

The Turn, or 4th Street in Holdem is the first step where the bets are doubled.

Use the information you get on the flop to analyze your relative strength in the hand wether you should continue the hand or not, trust your instinct.
If you were slow playing a monsterhand, now is the time to push your chips into the pot, to take as much as possible from your opponents.

If your on a draw call if you have potodds.

Bet on turn to prevent your opponent to get the river card for free.

If your opponents bets hard, seriously consider folding even if you have a decent hand, there are a good chance that you are beaten and even if you improve your hand you might be drawing dead.

River / 5th street

The river isn't as complicated as the flop and the turn.

Rarely fold on the river, there is a reason why you made it this far, either you have a good hand that you should valuebet or if you missed your draw. If you think your opponent also missed a draw you should consider a bluff.

Check on the river with a decent hand could be a useful thing to do.
If you think your opponents would fold if you bet then its better to let your opponents bluff on the river.
Check and call if you're not sure if you really have the best hand.
You should also have in mind the pot odds when you call on the river.