Are your trousers too long? Here is how to correct the problem without having to resort to having your body stretched out on a rack.
Get a friend. Hopefully one who has a ruler. A 6 inch ruler is best or a 12 inch one is okay but yardsticks are too long and unwieldy. This is important, as it's nearly impossible to get the correct length without one1.
Set up your ironing board and preheat your iron.
Stand on a stool or step. Ask your friend to mark the correct length with straight pins all the way around each leg as you turn around. No matter what length you decide to want your trousers to be, the bottom edge of the trousers should always be the same distance from the floor all the way around your leg - you can make sure of this with the ruler. It's important, because if you just cut them straight off just from one single mark/pin on the front, they'll always be slightly crooked, depending on the size of your bottom and/or tummy. Be sure to keep your hands at your sides when being pinned, either for a skirt or trousers. Each time you raise your arms, the waistband will shift which will affect the length of the garment.
Do not laugh at your friend because she/he looks so silly sitting or lying on the floor, trying to keep the ruler straight while trying to tell you 'start turning to the left' with a bunch of pins in his or her mouth. Not only is your friend doing you a favour but, when you laugh, your belly will shake and move altering the measurements and causing your friend to give up in disgust.
After your friend is finished, thank him/her, take off your trousers and turn them inside out. Fold over the material at the spot where your pins are placed, forming the inside of your hem. Take some more pins and pin the hem in place just over an inch from where your friend put the original pins.
If the trousers are very long, or you are slightly shorter than you thought you were, and your extra material is wider than an inch and a quarter, you may have to cut some of it off. But do not do this just yet!
Iron your new seam along the path of pins that your friend has made for you. You want a nice, straight crease here so go slowly.
It is easier to do all this with the pants turned inside out as you'll be able to see where all your pins are. Also, many fabrics, like fine wools and the ones made out of chemicals rather than natural fibres, should not be ironed unless the garment is inside out or without some sort of protective cloth between the fabric and the iron. If you iron these fabrics directly on the outside it wrecks them or gives them a funky shine.
Carefully turn your pants right side out again and put them on. Pin alert!
Stand on your stool or step and ask your friend to check to see if the length is even. You may have to make some adjustments. If so, just re-pin, inside-out and re-iron. Once your friend has assured you that one leg is not longer than the other, and that the bottom of the trousers is the same distance from the floor all the way around, iron again. This is a good time to cut off any extra fabric.
Sewing: don't run away! This isn't really complicated sewing, and you're not going to even need to use a sewing machine. Find some thread which vaguely matches the colour of your trousers and a nice needle. It is always better to use a slightly darker thread than the fabric if you cannot find one that matches exactly. Thread the needle and begin by oversewing a few stitches which will hold the end of the thread in place.
The trick to hemming trousers nicely is not to let your needle go all the way through to the right side of your trousers. You should push your needle and thread all the way through the short, tucked-under part that no one sees, preparing to make a nice loopy stitch at an angle to the trouser-leg. At this point, use the sharp point of your needle to pick out a thread or a tiny bit of fabric from the inside of the trouser-leg, not letting it go through to the other side. Then finish your loop and go on to make your next stitch.
When you've finished, don't forget to take the pins out and turn your pants the right side out again.
The sewing bit make take some practice, but once you master the trick, you'll be very proud of yourself.
Alternatively, if you don't have any friends, a ruler, or even if you think this is too much of a bother, you can go to your local tailors and let them do it for the outrageous fee of about US$7.00.