If the holes in your salt shaker are getting clogged, it's probably because the salt in the shaker is getting damp, so when it comes out it clumps together and gets stuck in the holes. This usually happens if you live in a humid climate. There are a couple of ways to fix this.

If you live in a dry climate, the salt is probably getting damp due to where it is stored. For example, if you store your salt over the stove, it probably gets damp from all of the steam coming off the stove. The easy solution is to store your salt somewhere else.

If you live in humid climate, the best way to keep your salt dry is to put something else in there to soak up the moisture. The easiest way to do this is to put in some dry uncooked white rice with your salt. This will absorb the moisture to keep your salt dry. But the rice kernels are too big to fit out the salt shaker holes. Plus if you have a clear salt shaker, the white rice blends in nicely with the salt to make it look less obvious.