http://sheldonbrown.com/brakturn.html Advice on braking technique Practice and you'll instinctively move your weight back and down as you brake. Also important to be very aware of your surroundings to minimize those panic stops.

http://sheldonbrown.com/gears/ A gear calculator that'll give you gear inches, gain ratios, and speed in mph at certain cadences (rpm) It's cheaper to swap cogs than chainrings. A 1 tooth difference on the cog ~4 tooth difference in your chainring. 48-18 = 70 gi 44-16 = 72.5 gi 42-15 = 74 gi for a bike with 700c wheels. The 70 gear inches will probably be a bit low; try the other two. My wife's mixte is 48-20 but she likes it that way. I started out with a 42-17 then switched to 42-15. I use brakes on the front and rear. Front only is fine but when I'm scrubbing speed on a downhill I alternate front-rear, front-rear. Rear brake isn't as effective at stopping you as the front but it will give you more control over the bike, particularly on wet pavement and/or twisty descents.

In fact, just read the entire www.sheldonbrown.com