Spades

Setting up your partner
Your partner can play a spade to win a trick in a suit if they show any of the following signs:
Doesn't follow suit when you win a trick.
Plays a very high card with no hope of winning the trick when there is no clear reason to waste it.
Bidding guidelines
Please note these are very safe guidelines, only intended for beginners.
An ace = 1 point
A king + another card in that suit = 1 point
More than three spades = 1 point each
More than four of a suit, apart from spades, negated one point per extra card
Partner blind nilling = 2 points
Bagging
You lose 100 points if you get 10 points over your bids in the game. To avoid bagging you should try to stick closely to your bid. Ensure that if you have got your bid covered, and there is no apparent cause to take any tricks for your partner, that you throw away all other cards, unless you want to set your opponents.
Table positions
Think about your position relative to other players, if you are nilling after another person has nilled then it makes it harder because their partner can decide what to do based on whether you have played a card higher or lower than them and it puts you at a great disadvantage.
Should I nil?
Definitely nil
Do you have 3 or fewer spades?
Do you have no high cards without at least 2 lower cards of that suit?
Are you missing the Ace of spades?
Vulnerable nil
Do you have a possible way to discard every high card? For example a low number of clubs could be a way to discard the Ace of diamonds.
Do you have 4 or fewer spades?
Covering a nil
If you play an ace then you know your partners highest card was whatever they played, therefore it is safe to assume all their other cards are lower than that.
If your partner doesn't follow suit then play that suit wherever possible so that they can discard any dangerous cards.
Try to avoid using your spades, unless it is to cover your partner or you know they have few spades, otherwise he may end up winning a trick with spades if he has many of them.
Setting
Setting your opponents refers to taking extra tricks so that they don't make their bid. To set your opponent you can either continue to take tricks because you got lucky or you can deceive your opponents during the bidding process. For example if setting your opponent is your only way of winning, then you can bid nil, causing your opponents to try and break your nil or bid more highly, and then start to take tricks.