There are two basic things to start with - whether or not you prefer foot retention. Foot retention basically means binding your foot to the pedal, whether that be with a physical "Toe clip" or strap, or using a "Clipless" system pretty similar to the technology used in ski bindings. The advantage in using some form of foot retention is an increase in the amount of power coming from your legs actually making it into the drivetrain, including on the upward part of your pedal stroke. It's also a little easier to settle into a cadence, which is a steady and continual number of pedal strokes. I'll go into more detail below on the differences and advantages/disadvantages of the various types of foot retention.
Platform pedals are the most basic, common type of pedal, but they come in a HUGE array of shapes and sizes. These are my preferred type of pedal on my Surly for two reasons. One, I own a huge array of shoes - waterproof boots, sandals, flip flops, tennis shoes, and fashion choices, and like to be able to ride in all of my shoes. Additionally, I personally have some joint-related issues and strapping my feet to the bike results in knee pain over time (yes, I had my clips properly adjusted on my cycling shoes when I used them). The reason for this is that clipless and toe clip pedals do their job extremely well and you can't move your feet around on the pedals, locking you into a single, identical pedal stroke. For my knees to be happy a little variety is good and so I am a sans-retention platform pedal user. However, if you take lots of really long rides (30+ miles) and don't suffer from the injuries I have, platform pedals do lose some efficiency.
There are a few main "styles" of platform pedal - rectangular is the most common type that comes on commuter bikes. I personally am quite fond of "BMX" shaped pedals with few sharp edges because I live out of sandals and shorts in the summer. Often, rectangular shaped pedals typically have sharp little nubbins designed to help hang onto your shoes, but I have destroyed shoes and cut my legs up too many times to count on these nubbins. But if you're one for long pants and consistently wear close-toed shoes, the rectangular pedals are extremely versatile and normally hang onto your shoes extremely well.
|Rectangular "rat trap" style|
Toe Clips & Straps
These could by and large be considered a modification or variation on platform pedals - it's the same thing with some strappy bits attached to it. These originated Way Back In The Day with racing-oriented road cyclists to increase their efficiency. They offer a sort of middle place between retentionless platforms and dedicating all the way to clipless pedals. They CAN be ridden in multiple pairs of shoes but I really wouldn't recommend them with sandals as they can scratch the living hell out of the tops of your feet (ask how I know). Many road bikes (at least the ones that come with pedals) come with these attached as a cheap way to get you up and running.
There are some more modern variations such as Power Grips available which don't have an actual "toe clip" and are basically just straps that mount to the pedals.
|Those guys are on the Tour de France, smoking cigarettes. |
However it's also a good picture of old-school toe clips.
Clipless are by and large the modern choice for sport cyclists and even many commuters. They offer extremely good efficiency, and are pretty easy to get in and out of once you've acquired the muscle memory. There are two basic types, "SPD"/"Mountain" and "3-hole"/"Road." They're primarily differentiated by how the clip itself mounts to the bottom of the shoes - Mountain style pedals have two holes in the bottom of the shoe for a small, low-profile clip, and 3-hole feature a much larger clip attached to shoes that usually have absolutely ZERO tread. 3-hole pedals should pretty much only be used with bikes primarily oriented around performance usage, rather than utility.
Mountain bike style clipless pedals offer a truly stunning range of style choices made by a variety of manufacturers. Some pedals even have a platform on one side and a clipless attachment on the other! Some can be clipped into from almost any angle by basically kicking your foot into the pedals - Crank Brothers pedals are specifically designed for this.
The other big advantage of mountain bike style pedals for the utility cyclist is that there are a huge variety of shoes made for clipless pedals designed to look normal. If you're a commuter and want clipless pedals, mountain is the way to go.
On a small aside, if you're like me and have some joint issues, two big metrics to pay attention to are "spring tension" and "float." Spring tension determines the amount of force necessary to pop out of the clip and on any pedal made by Shimano is adjustable. Start easy and as you gain more skill with clipless pedals increase the tension to wherever you're comfortable. Float is the amount of lateral movement allowed before popping out of the pedals - for me the only pedals that really worked for me were Crank Brothers as they had the amount of float necessary for me to avoid requiring reconstructive knee surgery after hours on the bike a week.
|Shadow, featuring Crank Brothers Candies.|