You can do a pretty thorough checking over of your body shortly before candle lighting so that you can remove any chatzitzot before Shabbat. Once you get to the mikvah you have to inspect your body again, but you can be confident that you did your best to remove all the chatzitzot before Shabbat.

It is important to remember that although we try to remove all barriers prior to immersion, many of these barriers would not actually invalidate the tevilah after the fact. That means that although we may try to remove small pieces of flaking skin, they would not invalidate the tevilah if you did immerse with them, especially if they were sufficiently softened from bathing. Tiny flakes of a skin are not even considered a chatzitzah, and you do not need to worry about them all. If you have specific areas that concern you (your nails, lips, etc.) you should give them particular attention before Shabbat, even smoothing them down with a light cream if necessary (leaving enough time that it will be totally absorbed by the time you go to immerse.)

B'Hatzlacha!