The most important thing in agreeing to any contract, whether it is an affiliate contract or any other one is to read and understand what you are agreeing to. Affiliate contracts are no different to this standard rule even if it is not usually something which you can negotiate.
Affiliate contracts are inevitably stongly weighted against the affiliate as it is the programs themselves who write the contract. The normal course is to either agree with the contract or not promote the program. I have not yet come across a program which has agreed to adjusting its standard terms and conditions unless the affiliate concerned is a super affiliate who is effectively opening a white-label of their site.
That said your main decision is to not promote the program and with the myriad of different affiliate sites which you can promote (admittedly this is less in the New Zealand affiliate market) you should still be ready to read the conditions and understand that you do not want to agree to them nor promote that site.
Over the course of the next few months I will endeavour to list the main stumbling blocks which affiliates find in their contracts, usually when everything goes wrong and they were not aware of their lack of rights.