Here is a good article I found by M.Holland
Zone Defense

This is a very effective defensive strategy, but requires the participation and understanding of the entire team. Zone coverage works just like zone coverage in football. That is, each player is responsible to cover a specific "zone" of the field. Any offensive players that enter your zone, you are responsible for blocking passes to them. If they run out of your zone, you drop off coverage and allow your team mates to cover them, picking up other players yourself.

Because a Frisbee "floats" more than a ball, zone coverage works better than in any other sport. Playing zone defense allows you to play off of receivers a bit more, because you will want to carry some momentum into a play on the disc.

If you decide to play a zone defense, it is important that you do not shift the zones as drastically as in football when the play moves to one side of the field. The disc in Ultimate is passed across the field regularly, so teams that collapse the zones are likely to be caught off guard.

Swing the Disc

"Swinging" the disc is one of the most effective ways to make deep passes. The basic idea behind swinging is that you throw a pass that is only catchable by your intended receiver, preventing an interception.

To swing the disc, you throw the Frisbee hard in one direction, with the disc slanted at a significant downward angle in the opposite direction. For example, you throw the Frisbee hard to the right with the disc at a 45-degree angle. The disc will fly off hard to the right, and hook back in to the left at the apex of the throw.

The swing can be very effective if played out of bounds. You can throw the disc from the sideline out of bounds so that it hooks back and slopes back onto the field of play just by the sideline downfield. If you have a player there to receive the pass, they will be the only one with a chance for a catch.

Play a Handler

The "handler" is usually the best thrower on the team and can be very effective in opening up deep passes. A handler usually plays toward the center of the field, and never advances beyond the position of the disc. The purpose of a handler is to receive a lateral or even backwards pass from a covered player in order to open up throws downfield.

Running through these simple strategies can greatly improve your game.

The four most used throws in a game of ultimate.
Forehand, Backhand, Thumbflick, and the Hammer