Sometimes you'll need the time of a busy person (like your boss or a person on billable work) for an approval, and you may find their availability limited.
You need techniques so you're not blocked, so here is a process you can follow:
For the above, your escalation path for something that usually needs a particular person should go something like this:
Tip #1: Use common sense. Some things may make more sense to try a few times with your boss before escalating.
Tip #2: Of course, some things really are big decisions that should not be escalated. But these should be the exception, not the rule.
Tip #3: Your boss will have some things they care about a lot, and they won't want escalated. Could be money related, hiring decisions, or their YouTube channel. Be aware of those.