A nominal dimension describes the size you are asking for. A tolerance describes the acceptable variation around that size. State both when the fit or a later manufacturing step depends on them.
Write the allowed range
For example, a requested length of 12.000 in ±0.010 in describes an acceptable length from 11.990 to 12.010 in. This is a notation example, not a promised cutting tolerance. If the variation is one-sided, show that explicitly.
Separate stock and cut requirements
Stock thickness and diameter, cut width and length, flatness, straightness, squareness and edge condition describe different requirements. Call out the ones your project needs rather than assuming that one tolerance covers every feature.
Allow for your next operation
If you will machine the blank later, specify the blank size and any required material allowance. Do not use a finished-part drawing without identifying which operations are included in this material request.
Get critical requirements confirmed
Attach the drawing and identify the critical dimensions. The reviewer needs to confirm whether the requested material, process and inspection scope can meet them before the work is agreed.