Measure your flooring area for width and length checking to see if you have a room that is out of square. You do not want to end up with small cuts of tile at the edges of the room. If you are using 12" tiles and your room is 11'2" you do not want 11 full tiles and a row of 2" tiles. Instead, use one full tile less, 10 full tiles, which would leave a 7" tile on each edge. Do the same for the length of the room. You only have to cut your tiles so they get within 1/2" of the walls because the base trim and shoe will cover the perimeter. This can help with walls slightly out of square.Next you want to section off the floor into four quadrants by using a chalk line and snapping two lines at right angles to each other. Using the 11'2" wall, at one end measure 5'7" (half the distance) from the wall to the center of the room and make a mark on the floor. Then do the same at the other end of the same wall. Holding the chalk line tautly across the two marks, snap the line so that you have a chalk line parallel to the wall 5'7" away. Let's say the adjoining wall is 13'9", which would give you 13 full tiles and 4 1/2" cuts at both sides. A more professional look would be to use 12 full tiles and have 10 1/2" tiles at the edges. You would then make two marks from that wall 6'10 1/2" away and snap the other line. You now have split the floor up into four sections.
Decide what size grout joints you want to have between the tiles. It is a good idea to use plastic spacers that will keep your grout joints consistent. Mix half of a 5 gal. pail with thinset mortar to the consistency of peanut butter. Follow the bag of mortar's instructions for which size notched trowel to use, but for most tiles a 3/8" square notch is good.
Starting at one of the corners in the middle of the room, start spreading the mortar out so that you come right up to the chalk line, but not covering it so that you can see the line to get the edge of the tiles perfectly along it. Spread the mortar so that you can work 2 rows of tiles at a time from the middle of the room down along the line towards the wall, using your spacers as you go. When you get to the wall, start back to the middle with two rows. When you get to a wall and you are nearing a corner, you want to fill up to the corner and work your way backward to the middle so you don't get stuck having to walk on newly set tiles.
All four sections are done the same, but you must plan out so that your final section has a doorway so that you have a way out.
A few tips: