Stay AWAY from automatic car washes with brushes. I ruined the paint on a midnight blue car once with one. It looked like I had used a brillo pad down both sides. Hand wash is always the best, being careful to wash starting from the top, going down. I prefer a wash mitt to a sponge, but rinsing it often is the key to preventing scuffing the clear coat with dirt.
A bucket like this prevents needing a second bucket:
http://www.ebay.com/itm/271319001020
Dirt will settle to the bottom and the grate prevents the mitt/sponge from picking it up.
Keeping a good coat of wax on the car year around is the best. Use a type that doesn't leave the white reside like Sickr mentioned. Bugs and bird poop have to be removed immediately (at least as soon as practical) to prevent paint damage. I try to pay extra attention to the front of the car when I'm waxing and give it an extra coat. I like to use a wash & wax concentrate instead of just detergent when washing to prevent washing off the wax. After getting most of the water off the car, I also like Turtle Wax Wax & Dry spray (or something similar) and a microfiber towel to finish.
For me, the bay wash with the high pressure spray is a last resort. I've used them when I was away from home to remove bugs, road grime, mud from wheel wells etc, but it doesn't replace hand washing. Be very careful with a high pressure sprayer as it will cause stripes and decals to lift if you get too close. Stay away from weather stripping around the door windows too. You can do a lot of damage with over 3000 psi.