Studio equipment is a very competitive market so you'll rarely have to pay the manufacturer's list price for anything. You can always find someone who'll give you a discount, so shop around. You'll often find that you get further discounts if you buy a package of two or three items at once or if a product is about to be discontinued.
Ideally, you want to be able to try out the equipment in the shop but this can be quite tricky - especially in a noisy shop. Generally, try and get along mid-week when the shop will be quieter so you can actually hear things.
Take along something appropriate to try it out - your singer or an instrument if you're buying microphones, or some of your favourite music if you're buying speakers.
See if the shop will let you book an appointment - it can be difficult to flag down a shop assistant on a weekend and the queues to try out popular bits of gear can be long.
Most shops will do mail order so you're not limited to using your local store. It can get a bit messy if you miss the delivery van, so make sure you specify an address and time when you know you'll be able to receive the goods.
Many shops offer a home trial period so you can exchange the item for something else if it turns out not to be the one for you. This is the ideal way to try out equipment. Actually trying to do some work with it will give you a much better idea of whether it's right for you than a demo in a shop will.