Help with cat please.

A lot depends on what type of cat you're talking about.  Cats which have skegs (like Dart 15/16/18) or have assymetric hulls (like the Hobie 16) will tack pretty slowly and do like to have the jib backed to blow them round onto the new tack.  Cats with boards (like the Spitfire, Stealth, F18s etc) will tack much more quickly.  Many of the latest boats have a self tacking jib so you can't back the jib anyway - and there are plenty of singlehanders that don't have jibs anyway.

Important things which I've learnt since I started sailing a cat:

• go into the tack fast - if you're trapezing, you need to start the tack and then come in off the wire, not the other way around
• move weight to the back of the boat and stay on the original windward side until the boat is through the wind on the new tack
• ease a lot of mainsheet as the boat goes head to wind
• if (when) you blow a tack, steer the opposite way so the boat will reverse out of irons onto the new tack.