A good step to take early on is to write down the form that the solution is going to take. That is, if the final result is going to be some amount of currency, make a place for that,

solution:  _________ dollars
Likewise, if it's going to be a set, or a point, or an equation, or a time, or a ratio, make a note to remind you of that,
solution:  { , , ,}

solution:  ( , )

solution:   __:__:__ 

           height of triangle
solution:  ------------------
           radius of circle
Then when you think you've found the solution, if it doesn't make sense in the place you made for it, you know you have a problem.

A second benefit of doing this is that it forces you to pay attention to what the problem is asking for, before you get wrapped up in the details of the problem.