The golden rule for tiling is to use full tiles as much as possible and hide cut tiles.
On tile countertops, grout lines and cut tiles will be very visible so it's important to spend some time planning your layout.
You want the edge of your countertop to be laid out symmetrically since, in most cases, both sides will be visible.
First find the center point of the edge and draw a line down the middle perpendicular to the front edge. Using that point as the center grout line, lay out your edge tile in both directions. Be sure to account for the thickness of grout lines between each tile.
Check the size of the cut tiles at the end of the rows. You never want these to be less than 1/2 the width of a full tile. If they are, adjust the center line 1/2 the width of a tile in either direction. This means instead of having the grout line at the center, you'll have a full tile centered on your center line.
Draw a new reference line on the side edge of the center tile.
Lay tiles along your reference line to the back of the countertop. Again, allow spacing for your grout lines.
If you're using edge tile, most likely you'll want your cut tiles in back.If you're using a regular field tile or bullnose tile for the front edge, you may want to have equal cut tiles at the front and back of the countertop.
Mark the back of the last full tiles and draw a perpendicular line through your other reference line.
Do the same with the last full tiles on the sides and in the front. These will help you keep the full tiles in line.
You should also draw reference lines for the last full tiles on both sides of your sink cut out.