Basic Bike Fit Tips

[AlfaFoxtrot]

Been commuting to work (4 miles each way) on a 1980's steel framed roadbike, with the odd longer ride out into the countryside if the weather's alright. I use cleats (Shimano mountain bike SPD as it means I can have a flat pedal on one side for nipping into town/pub), and have had zero problems with it for the last couple of years.

Recently bought a posh road bike, fitted SPD pedals to that so I can use the same shoes. Really enjoy using it, and have started doing longer rides at the weekends (50-70miles). After some initial fiddling with the saddle height, I haven't given any thought to the geometry, as aside from a sore arse (primarily due to time in the saddle) there were no problems. Last weekend though, I did a hilly 70miles and now have got some 'twinges' in my right knee whilst doing the weekly commute. I'm 26 and fairly fit, so although I have upped my average weekly distance noticeably over the last couple of months, I'm worried there's an angle wrong somewhere and that I'm damaging things...

So I'm now weighing up a few local places to get a proper bike fitting, but most have got a few weeks waiting list. In the meantime I'm happy to avoid longer rides, but if there are any changes I can make to reduce extra damage to the knee during the (unavoidable) commute that would be nice. Having done a bit of reading it sounds like cleat angle and saddle position (forward/back) are some of the most common - any general tips for these bits or other parts of bike geometry?

[AlfaFoxtrot]

Looks like I've got some reading to do! Thanks for the suggestions so far. I'll aim to make whatever modifications come out of the various sources and try it out on some easier ride. If I still have issues I'll consider a proper bike fit.