I don't know if there's any consensus as to the ideal float number, but I think that most beginners should have at least some amount of it. No-float cleats are frequently blamed for knee injuries--whether this is true or not I don't know, but it makes intuitive sense to me, because you cannot make small in-ride adjustments in foot position without some float. If your position/technique is imperfect, having no float would seem to exacerbate the issues.

"Some" would be 15 degrees. The more "float" you have, the more you will have to twist your foot to get them out of the pedals. More float (> 15 degrees) is more forgiving of lateral foot/heel rotation in/on the peddles. I like more float because on long ride I jimmy around with my feet and when I climb I tend to really twist around a bit and don't want to pop-out on a downstroke. Crash! Never have yet on my speedplays.

Less float (< 15 degrees or fixed) means your foot does not need to rotate very much to 'clip out'. But it also means that even the slightest foot rotation means popping out of the pedal. Less float needs only a slight heel twist to exit, so you'll have no worries about getting out when you need to, so THIS strategy might be better of newbies. You can argue either way. However, I too have heard that fixed puts torque on your knees since your feet cannot rotate laterally on a fixed pedal (so the torque travels to the knee). Some would say that more float is good for newbies also because it is a relaxed pedal-to-shoe connection. Also, high-end pedals can adjust the float. If $ for peddles isn't an issue, I'd track down some adjustable float pedals that let you choose either 'locked' or 15-degree.

FYI - I am still riding on the original pair of 15-degree float 'lollipops' I bought five years ago. Pedals last and last and last so invest for the long-run. Also, check for weight limits on pedals, and I would recommend double-sided entry.

The average pedla is going to be in the same neighborhood as Look and Shimano- around 6 degrees. This is pretty "average" and if you do not have outstanding knee issues. You can adjust the release tension loose or tight, and it will hav enot bearing on the amount of float. Loose settings are good for newbies as you can get out easier, but the pedal will still reward correct entry and exit with a audible click.

Speedplay is unique in its design. I personally do no like their pedals. Yes, they have double sided entry, but I do not like the entry or release mechanism, and the float is a bit much for my taste. They can also be very pricey for the medium level pedals. I would recommend waiting for these untill you are a little more experienced and more able to determine if you want to give them a go.

Speedplay "Zero"s and "Light Action" pedals only have 15º of float... it would seem a good compromise between the 25º+ float of Speedplay X series, or the 9º max of Look Keos.

I have been riding on my clipless pedals for about a year now with a fair amount of float (I'm not sure exactly), which a prefer when I'm riding, but I am still guaranteed to make a fool of myself at least once every other ride by falling because of the pedals. Yesterday I approached a stop light and unclipped on one side and sure enough I lost my balance and fell to the side that was clipped in. Of course with the high degree of float, my foot doesn't release quick enough and down I go. Mostly just an ego bruise, but once I did it in front of two women who chuckled which was far more damaging to my ego than the dude on the Harley yesterday :-(