This one I am pretty good about! I decide on my budget for the year, do a rough outline of where I think the money would be best spent, and sit down with my pro and go over it. He usually starts with the number, does his own version, and then we compare. Since we have done this a couple of times, the allocations now end up pretty much the same. I will acknowledge that when I set my budget, I set it a few thousand low, knowing that I will easily find a good way to spend those last $$$. It gives us a little flexibility during the year as well.
I'm putting all of this out here because most people seem to not do it. It was--humorously--listed as a good student attribute with a visiting coach and the coach's reaction indicated that it is not a widespread practice. I'm actually a little shocked at how much I can spend without it directly increasing my teacher's income. First time we did this, for example, he wanted me to allocate some of the budget to new dresses. He also has a better idea that I would have of how much to allocate for visiting coaches. This only works if most of your dancing $$$ get funneled through a central point, but it has helped me a lot. Pro isn't having to always ask me if I want to do X or Y and my decisions are make with a good overview, rather than in isolation.
(I hope this all makes sense, not enough sleep last night….)