Before signing a home improvement contract you have to do some homework on the work of a contractor. Ask for references or ask your friends or colleagues for names of reliable contractors.
Also enquire if the contractor is licensed, or whether the licence is still valid. Enquire about any possible complaints about the contractor.
Once you have chosen a reliable contractor, make sure that the content of your contract is extensive and covers most applicable aspects of the work that needs to be done, e.g. terms and conditions about the payment and supply of material, as well as payment dates and possible retention amounts on the completed work.
Your contract should include full personal information of the contractor, his license number and the dates on which he will start and finish. It should include a "right to terminate" agreement, which gives you approximately 3 days to change your mind should something unexpected should take place. Make an arrangement to pay in down payments and not to pay the last payment until all the work is complete and all debris has been cleared and removed from your premises.
State whether the contractor will use your facilities such as your toilet, telephone, or whether they should provide their own. Ask questions if you are uncertain about anything on the contract. Do not sign the document unless it has been fully completed by the contractor and keep a copy of the signed document.
Be extremely careful and you should have the least problems.