Scuba Regulators

The better dive shops will quite often allow you to 'try before you buy' during their pool sessions, or exchange gear that's not quite right (assuming you haven't damaged it)--that's part of what makes them a 'better' dive shop. Obviously this does not hold for second-hand gear, and usually not for Internet dive shops either (check their refund/return policy first).

As far as second-hand gear goes in general: check your source. Do you know them? Do you trust them? Can they show that the BCD/regulator/whatever has been well looked after? It might be worth thinking about buying ex-club/diveshop rental gear, as that will be cheaper than buying new, but it still has to be 'saleable' (i.e. maintenance has to be documented, and you have legal protection against being sold shoddy gear), Again, the 'better' shops/clubs will renew their gear regularly, so it shouldn't be too battered.

As with most purchases, going for major brand names assures a certain level of quality and even though many of us like a bargain, with Scuba equipment, the more you spend the better the equipment you get. So, if you thought your regulator would include an octopus and gauges, take your regulator budget and deduct between 30% to 40% to allow for the basic instruments you will need. Whatever is left is what you can afford for your regulator.

You should always use the same brand of 1st and 2nd stages, plus the octopus you choose should also be from the same manufacturer as your regulator to ensure the intermediate pressures are compatible. Gauges need not be made by the same manufacturer but you should always go for major instrument brands because their accuracy and reliability are much higher than imitations.