Constantly update expectations based on how the work is actually going and based on evolving requirements. If you are T&M or Fixed Fee, you need to always give people your best expectation of progress and where you think (even with a lot of uncertainty) you'll be when the budget runs out. If you do this constantly and early clients feel empowered to make choices (including adding more budget). If you just work until the money is gone either you eat the overage or the client is blindsided and pissed off.
The short version of this: Never, ever, go over budget - always ask for more money or a cut in scope and always do so as early as humanly possible.
If you and/or the client aren't clear on scope or if the budget is enough, don't sleep at night, confront and squash the uncertainty and resultant misalignments or you will get bitten!
The short version of this: Never, ever, go over budget - always ask for more money or a cut in scope and always do so as early as humanly possible.
If you and/or the client aren't clear on scope or if the budget is enough, don't sleep at night, confront and squash the uncertainty and resultant misalignments or you will get bitten!