Check it does what it should
If you buy a product, check for damage and missing parts as soon as possible — on the spot, or as soon as you get it home. Make sure there's no damage, check it works and it does what you have bought it for.
If you buy for a service, keep tabs on how the service is provided. Make sure it's being carried out the way you have agreed, and if not, speak to the service provider as soon as possible.
Refund, replacement, repair
Poor quality or incomplete work