* Check for a website and feedback. If the company is reputable they will have a website and a lot of good feedback.
* Make sure there are no hidden charges. Ask for their terms and conditions of hire.
* Check the quality of material as you don't want to be able to see the chair through the chair cover.
* Remember you get what you pay for. If they are cheap, their products are probably see through and aged.
* Ask if they replace their linen on a regular basis to ensure quality.
* Check that 'fitted' chair covers will fit your chairs. Ask for measurements and compare them to the chairs you are using.
* Lycra (stretch) chair covers can cause static in your guests lovely clothing. Ask if they use an anti static product.
* Most important of all, if you have questions don't be afraid to ask, ask, ask!