Well I am not an amazing player but I hear the advice that many of them give, much of which has been said already.
Don't think long and hard about obvious moves which you already calculated or where there is no real alternative, these should be played fairly quickly.
Learn to recognise the critical position where you have to decide the line you wil go down or commit to a plan of action. You should have put time aside for this point (normally after development when you are formulating a plan)
Think about the general position while your opponent is thinking.
You should know roughly the amount of time you have per move and budget it.
When selecting moves use a process of elimination and when you have eliminated a move as having an unsure resulting position or where you cannot see a definate mate there etc don't dwell so much on recalculating it many times.
Don't think long and hard about obvious moves which you already calculated or where there is no real alternative, these should be played fairly quickly.
Learn to recognise the critical position where you have to decide the line you wil go down or commit to a plan of action. You should have put time aside for this point (normally after development when you are formulating a plan)
Think about the general position while your opponent is thinking.
You should know roughly the amount of time you have per move and budget it.
When selecting moves use a process of elimination and when you have eliminated a move as having an unsure resulting position or where you cannot see a definate mate there etc don't dwell so much on recalculating it many times.