Along with following up on your tasks, being bold enough to ask the questions you need to know is vital to each and every project you complete. If you are not willing to ask questions, you may end up doing the project all wrong and have to spend more time fixing it than the project budget was worth. You also don't want to end up in a position where the client does not think you can handle the project, therefore gives it to someone else.
Like anything else, there is a fine line to asking questions. You want to make sure you do the work and read all of the project outline before asking questions. I know from experience. For example, clients don't want to hire you when you give them a roundabout estimate on a project that clearly lists the page count/word count—especially when that information is in the title. I bet that you have already guessed that job was not awarded to me. It was silly of me to ask how many pages when the information was clearly there.
However, if something is unclear, it is important to question it politely. In most cases, clients are more than willing to give further explanation. After all, they are paying you for a specific job—they want to get the most bang for their buck.