If you are submitting something to a review agency, they may limit which scales are acceptable, and you may need to request permission to use something other than a "standard" scale. A "standard" scale is anything that can be measured using a normal six-sided engineer's scale, which works well for all of the following:
1" = 1'
1" = 2'
1" = 3'
1" = 4'
1" = 5'
1" = 6'
1" = 10'
1" = 20'
1" = 30'
1" = 40'
1" = 50'
1" = 60'
1" = 100'
1" = 200'
1" = 300'
1" = 400'
1" = 500'
1" = 600'
etc.
If those really don't work, then the "fallback" is to use something that can evenly-divided into an existing scale. And in that case, it is best to try an make it a multiple of 2 from one of the "standard" scales. In other words, 1" = 80' (2 x 40) is preferable to 1" = 90' (3 x 30). This practice is generally discouraged in plan sets or plats (if not prevented outright by the reviewing agency), but it can be ideal for "lesser" drawings and exhibits in some cases.
But again, this is just the general rule-of-thumb. If you are submitting drawings somewhere, or if you are following a standard, you may be constrained in what you are allowed to use.