If you're following the video here for the long tail cast-on and doing as it's done, there will be 2 stitches on the initial cast on (since the way it is demonstrated doesn't use a slip knot though you can start it with a slip knot.) Make sure you're counting the actual stitches on your needle and not the number of times you make the motion of casting on.
If you are ending up with 2 extra stitches on your row , then it sounds like you may also be twisting the first stitch, which can make it look like there are 2 stitches on the needle when it's actually one. Sometimes the loop will come up around the needle on the first stitch, since it's looser on the needle
Good luck!