New cyclist - question about pedals

If you have knee issues be sure to get cleats and pedals that allow enough float so that you foot can be free floating but doesn't allow your foot to come free from the pedal.
For me personally, pedals aren't really important, its the shoes i buy that make or break a bike ride. Your feet have to be comfortable and the right shoe makes the world of difference. Like running, be sure to get a shoe that fits your foot.

If you are planning on using platform pedals I would recommend Cannondale Grind pedals. These work very good with sneakers. The replaceable studs in the platform grip really well. The platform area is quite large so you have almost an infinate amount of riding positions. You can use your running shoes as riding shoes so you wont have a need of getting more shoes.
If you are looking to clip in Look makes very good pedals. The Look Keo Easy pedal is reasonably priced and is good for entry to intermediate level riders. If you do go this route as previously stated make sure you get shoes that fit.

A moderately priced pedal works fine. A high end expensive pedal weighs less.

Agree with davereo's suggestion re Look KeO's.

Thanks for the input everyone. I'm definitely planning on going with a set of clipless pedals so I will take a look at the Look KeO Easy pedals.

If you are going to do a tri, then I would go with Speedplay, no question. There is a reason that most of them use them. They are a stomp and go style and after a little learning and break in by far the easiest to use. They have great customer service and you don't have to spend a fortune either. The tri choice by far is the Speedplay zero, and that would be my suggestion.

Most Triathletes don't need to clip in and out. Most of them leave there shoes connected to the bike.