1.  Give your opponents a chance to make a mistake.
Everyone does it, even the best players.

 2.  Be nice to your partner.  He/She will concentrate better.

 3.  Do not 'mastermind'.  If your partner is not good enough to share 
in the decisions about bidding and defense do not play with him/her.

 4.  Know your partners limitations.  If your partner is too 
inexperience to know how to play 'upside down reverse Rusinow leads' he 
will probably mess it up.  It will be your fault if  you talked him 
into playing it.

 5.  The 'kiss' system is best in casual partnerships.  Having to 
remember several unfamiliar conventions is too distracting for one 
session of bridge.

 6.  If there is only one way of making a contract, try it no matter 
how unlikely it is to succeed.

 7.  Know your opponents.  If they always bid one more than they can 
make, push them to that level.  If they frequently underbid do not 
push.

 8.  Tend to take finesses into the weaker defender.

 9.  Count.  It is not as hard as you think.

10.  Always remember that if your partner is stupid,  you are stupider 
for playing with him/her.  If you tell me about how bad he/she plays, I 
will know that you played with him/her.

11.  When defending, if you have a bust hand and your partner has a 
good hand, give very good signals;  however, if your hand is so good that your partner probably does not have an entry - do not play true cards.