Best bit of kitchen kit ever! This book is really well worth investing just a couple of quid in for a second hand copy, covers all the basics and should get you off to a good start.
Amazon.co.uk User Recommendation
The only times I ever pre-cook anything are browning mince for bolognese sauce or cottage/shepherds pie. Depending on how big your cooker is, it's always worth doubling up the potfor the freezer too, so you have a meal now and maybe a pie filling for another day. Just think slightly differently about how you organise your menus and the machine will really help you with time and money.
And don't be afraid, slow means slow - I've put some beef in guiness in just on the warm setting tonight, and it'll cook for 24 hours happily. Flash chefs call it sous-vide and charge the earth.
Tilley, most of the supermarket chains sell their own "basics" range 2.5l version for 15 to 20 quid, in brushed aluminium, with high, low and warm settings - keep the old one for that killer festive mulled one though!