Do I need to "tune-up" my mountain bike?

First of all you really need a tune-up. Go to a good local bike shop to get one. Second, after the tune-up ask them how to keep your bike healthy. They know the local climate and road conditions better than we do.

Johnpowell said it all. Do exactly what he said.

what entails a bike tune up?

bikes are not complicated. aside from keeping the brakes tight, the gears oiled, and the tires full what is this bike tune up?

Actually, there’s more to it than that. A good bike mechanic will check:

1) front and rear derailleur adjustments
2) brake and shift cable tension
3) trueness of the wheels
4) spoke tension
5) the looseness or tightness of the hubs
6) headset tightness
7) brake pad wear
8) bearings (usually for an overhaul, not a tune up)
9) and then the uncomplicated things like air pressure and lubing up parts that need lube
an
Did I forget anything?

Anyway, bikes are a bit more complicated than you might think.

most of those checks are something that involves the tightening of a nut / screw or replacing the whole part. The cable is for the gears is loose, you unscrew the cable, pull the wire and screw it back in. the brakes are old, two screws and two pads. the spokes are off, your getting a new wheel right?

I’m not saying that he shouldn’t a tune up, but if your mechanically inclined you can do most of that work with out much training.

i disagree. i think people who dont know much about bikes should not be doing their own mechanical work. a good mechanic will tune your bike in such a way that you REALLY feel the difference…... tuning it up every 6 months (or more!) is a good idea!

True. Even if you are mechanically inclined, most tools for working on bikes are bike-specific. You might screw up your bike if you try to use regular tools on it.