think about it, for whatever speed your running, for a certain gear, theres going to be a certain RPM the engine runs at. The purpose of the clutch and syncros is to match the speed of the transmission gears to the engine/flywheel. if you can match those on your own, the car slips into gear fairly effortlessly. For upshifts, (and this is easier to do at higher RPM's). You accelerate, let off the gas, pull the car out of gear, and as the rev's drop to the right speed, start applying pressure to the next highest gear. to downshift, you lift off the throttle, pull the car out of gear, blip the throttle to the revs for the next lowest gear, and start applying pressure on the stick. If everything is done right, it pops right in, usually with a little thud. (its hard to match it perfectly). More often than not, if you're not used to doing it, you'll grind a gear here and there. But with practice (in my case, a 89 chevy s-10 pickup) you'll become pretty smooth. Some old trucks almost require it, since the syncro's dont work so well anymore, or never existed. My jeep truck wouldn't go into first at all when i first got it the syncro's were so gummed up.