My son has a very dry scalp with quite a bit of dandruff. The winter weather makes it worse and his flakes are actually sticky - they don't brush off that easily. But they are flakes.
Usually dandruff brushes away. For those times when the flakes stick to the hair, how can you tell that it is not nits (lice eggs)? Well, eggs are very uniform in size and shape - ALWAYS the same and they are always glued to the hair. Dandruff can be very different in size and shape and usually can be easily brushed or blown away.
Also, if you have nits, you probably have bugs. If you have nits, go looking for ma and pa bug.