Buying bass drum pedals.
These days, there are so many pedals on the market, all doing different things, that it’s difficult to know what to choose.  There are a few crucial criteria to look for, whether you’re spending a little cash you’ve saved up, or blowing a whole load on something which you have had your eye on for years.

Pedal construction. 
There are a few things to look for in the pedal construction before you start thinking about playing it.  Many people favour a solid plate on the bottom of the pedal, which gives a great deal more strength, and a solid plate is generally a sign of a well-made pedal.  On slightly cheaper pedals (and some expensive ones too), more often than not a solid base is replaced by a pair of trusses along either side of the base. These save on weight, and are often as satisfactory as having a solid base. 

Next to look for is the chain.  Pedals either have a single chain, a twin chain, or often even a nylon strap (or other similar material).  A twin chain will often give a smoother, faster feel and more strength as opposed to a single chain, but with modern engineering, many manufacturers can get just as much strength and speed into a single chain pedal.  Strap drive pedals are a specialist choice among many people, who find they prefer a slightly smoother, quieter action.  Also many pedals feature a tension bolt which can change the tension of the chain, therefore changing the angle of the beater, which in addition to tensioning the spring, gives a good level of adjustability.  More advanced modern pedals also often include markings, so that you can measure your settings from spring and beater tension.

One final thing that differentiates many pedals is the beater itself.  Some have full felt beaters, some have two-way beaters with felt and plastic, and some even have three-way beaters with felt, plastic and wood (mostly on certain Mapex pedals).  This depends on the sound you are looking for.  Felt gives a full, round sound, wood gives a sharper punchier sound, with plastic somewhere in between the two.  Beaters can be easily changed however, so you can easily adapt to your preferred sound.

After this, it all comes down to how the pedal feels to you.  Think of a few pedals in your price range, and try a handful to see how they compare.  As with many things the “you get what you pay for” rule applies, and the more expensive the pedal, the likelier it is to last longer and have a nice smooth feel.  If you cant physically try out a pedal in store, just look for some of the features I have mentioned, and at the recommended pedal list below, and rest assured you will get something you will be happy with!

Double pedals.
Many manufacturers offer double pedals which match their single counterparts.  The thing to look for is whether the “slave” pedal matches the feel of the main pedal.  However, don’t be put off if when trying one out they don’t match exactly, most pedals take some adjusting before you can get them the same.  After this, the criteria the pedal has to meet is effectively the same as in a single pedal.

Do you use protection?
As the demands on your pedal become greater it is absolutely essential to protect your pedal during transit.  Simply throwing the pedal in your hardware case with the rest of your stands can have disastrous consequences!  Many of the top pedals come with cases, most notably the Tama and DW pedals, which have excellent hard-shell cases, and many come with semi-rigid cases, which are equally as good.  It may sway you to a particular pedal if only one of the two you like in the shop has a case.  If your chosen pedal does not include a case, invest in one to protect your pedal, and this may not necessarily be very expensive, so a worthwhile investment.

Recommended pedals (where no specific info is listed, both single and double pedals from the range are recommended):
On a budget:  Mapex P320 (or P380 double version).

Mid-range:  Mapex P550 (or P580 double version), Mapex P750 (available as single pedal only), DW7000, Tama “Junior Cobra” HP200, Sonor 400 Series, Pearl P900, Premier 4000 Series.

Top-range pedals:  DW 5000 and 9000 pedals (which are virtually the same although the more expensive 9000 is made from titanium), Sonor Giant Step (a broad range of different, all excellent, pedals), Mapex P950 (or P980 double version), Pearl Powershifter Eliminator, Tama Iron Cobra.