How much you have to spend?
Do you want only Free To Air FTA channels?
What satellites you want to receive?
Do you have any foreign language preference as some satellite cater better than others.
Do you want to program cards?
Do you want to use CAMS?
Do you want a motorised system?
Do you want a one stop box like the DreamBox?
If you want a DreamBox to get the best out of it you wil need an understanding of computers. A broadband connection would also be an advantage.
Then have a look in What Satellite magazine or similar for a general list of receivers and narrow it down. Check for those and others on the Internet where prices are sometimes lower.
Come back and ask for more advice - hope this helps and happy hunting!