For this technique the colours not in use are carried loosely across the wrong side of work so as not to distort the shape of the stitches being knitted.
On a knit row, hold the first colour in your right hand and the second colour in your left hand. Work as normal with the first colour, carrying the second loosely across the wrong side of work.
If you find it awkward to hold the yarns in both hands, simply work as usual, dropping the yarn not in use and picking it up again when required, making sure that it is not pulled across the wrong side. Always carry the same colour across the top throughout the row for a neat appearance on the wrong side, and to avoid the yarns becoming twisted.
When the second colour is required, insert the right hand needle into the next stitch and draw a loop through from the yarn held in the left hand, carrying the yarn in the right hand loosely across the wrong side until next required.