Some Golden Rules
Golden rule 1 - Never pay for an agency to help you, they get a huge fee when they place you and that is what they (should) earn their money from.
GR 2 - If you get asked to come in for an interview then ask if you will get your travel expenses paid there and then. If they say no then ditch them.
GR 3 - Do some homework. I see jobs advertised and if I can work out who the company is (Google is wonderful for this) then I apply direct.
GR 4 - If one agency has the same advert, usually word perfect copies, but in several locations then it is a trawl to get CV's in, don't waste your time with these.
GR 5 - Don't waste your time by applying for jobs you either can't do or don't want, you are unlikely to make it to the interview stage and you would hate the role anyway.
GR 6 - Smile, be happy, stay positive and don't give up.
Would anyone like to add to the rules?