It is not too hard...I would differ with the advice above - go to a friend with a powerful car, and ask him/her to teach you - it is much harder to damage a powerful car's drive train with poor clutch technique than it is in a pipsqueek car. Don't go for a competition car however, they can be a little tricky.
Have your friend show you a gentle start, followed by normal or "easy" shifts up and down through the gears, paying attention to the sound, and the RPMs if he/she has a tach. Then ask them to demonstrate a "hard launch", and watch the RPMs and the sound when done for maxumum performance. There are a lot of things going on in these launches, so it will take a lot of practice to get it right. It would be cool to offer your friend some money towards his/her next clutch job at this point. Clutches are wear items, just like brakes, and when you do a lot of this type of training, it takes some of the available life out of the parts. A clutch job can cost as much as $1000, and is commonly around $600, so an offer of around $200-500 is fair. You can't learn this on a rental car anymore, so this is the only way to do it.
If you can, ask friend to take you to a puddle or wet spot, and demonstrate what happens in low traction starts - important in rain, snow, or on sand and gravel.
Later, when you are comfortable with just getting around, ask a friend who knows, how to "Double Clutch" on downshifting - it is an essential skill for high performance driving, and besides, when well-done, it sounds SO cool. If you can get that down, so that it is really smooth, you will have mastered the skill.
It used to be mandatory to learn a technique called "Heel-and-Toe" (even though it is not usually done that way), but in recent years, there is some difference of opinion amongst racers. Jackie Stewart, among others, insist that the gearing and differential designs are not meant to absorb so much horsepower in reverse or retarding direction, and they just use the brakes to slow the car, slotting directly from sixth to second, for example, to set up for acceleration from the apex of a slow turn. Others say that the skill is still necessary, when on a downhill run in mountain driving, to get the brake temps down for the next braking job. I'm in the second camp.
If you can double clutch smoothly while braking hard, you are now ready to go to driving school, with a proper race car.
Automatics or "slushboxes" are costing motorists 2-5% in fuel economy. If you want the ultimate in fuel mileage, you need to drive a manual.
Regards
Guy