I am installing threshold between a bamboo floor and tile, and the threshold sits too high above the tile. I would like to use a hand plane to reduce it. But I have never used a plane before, and would like to know the correct way to use it?
The concept of a plane: It uses a very sharp chisel like blade mounted in a body to remove a thin layer of wood. In practice, you use both hands (for control and even pressure) to slid the plane in the direction of the wood grain to remove a thin layer of wood at a time.
For effective use, you will need the piece of wood you are planing to be firmly held in place. Use clamps, not someones hands, to hold the wood. The blade on the plane needs to be razor sharp (reason for not using hands) to effectively grab the wood and shave it. If it is dull, it is just going to skip and mar the wood. You will need to find the right amount of pressure you will need to pressure to keep the blade in the wood. Also don't try planing off too much at once. The deeper you set the blade, the more likely it will mar the wood. Start razor thin at first and gradually cut more as you get used to it.
For best results, do full strokes along the wood. Where you start and stop it is easy to create mars in the wood. Also if you do short strokes it is easy to create an uneven cut. A good way to see if you are cutting evenly into the wood is to create a scribe line where you want to plane the piece to.
As @Keshlam said in the comment, use some scrap first.
This is sort of a two part question. 1: How to fit a threshold, and 2: what are the basics of hand plane use. On the first point, place your threshold in its space and mark or scribe your piece, then remove it and tune the piece to the line. Trying to fair it out in place will likely result in either damage to your tile, bamboo, or plane. On the second point...that is a looooong answer. I've been actively studying the use and maintenance of hand planes for over a decade and am only recently starting to feel like I'm getting the results I want. I will tell you that the first thing you need to know is how to sharpen your iron, a skill that takes time to learn and if you want to get to really serious about it you'll eventually need to invest significantly in your equipment (my stones alone cost over $500). To be perfectly honest, unless you intend to get into furniture making, a power plane and a belt sander will do everything the average person wants to do with only basic skills and a fraction of the monetary investment. I personally recommend Bosch power planes and Makita belt sanders particularly the 9904 (it has a lower center of gravity and just feels right in my hand). Having said that, there is nothing more satisfying than the feel of a well tuned plane taking a perfect shaving. In that spirit, if you still want to pursue learning about hand planes check out the videos on YouTube by Peter Sellers and Rob Cosman, they cover a good cross section of what you'll need to know to sharpen, set up,and use hand planes.