I use a GPS to ensure I don't get off of the claim. I use a Garmin GPSMap66st and it works great for me. What I do is upload all of the claim corners and the center of the claim and also download Satellite imagery to my GPS before arriving at the claim. The satellite imagery gives me an idea of what areas are off of the claim and not. At the claim, while I am moving to a new spot I will occasionally glance down at my GPS and see if I am still on the claim, once you find a good spot and it's in the claim boundaries, you don't really have to worry about if you're on the claim or not as long as you're not moving all over the place.
It's also worth noting that researching the area around the claim can prove useful in determining if there are any other claims nearby and what land is private or BLM land.