In no particular order, these are some of the tools I use to get to an end result:
When a project statement is first presented, immediately sketch out the first zygotes of ideas that come to mind. They may not appear relevant in the beginning stages, but towards the end of the process looking back on them can be very useful.
Create an inspiration journal, scrapbook, computer file, box, or all of the above. Add to it constantly. Pieces of magazine, concept art, stuff that grabs your eye for whatever reason. File each thing in a way that makes sense to you.
Artists' and designers' work and living spaces are inherently a huge mess. Boxes, folders, jars, binders and envelopes can help keep the piles of junk from seeping into one another. LABEL EVERYTHING. add the date of the last time it was organized.
You never know when inspiration will find you. Have a camera as much as possible.
go for a walk.
Before starting a project, take a walk, preferably to a place you don't go to often. The change of scenery will dilate your senses and help with fresh ideas.
do a lap.
If you've been intensely working on a project for hours, stop and walk around for a bit (or roll your office chair around the house/studio with ski poles!)
A fresh pair of eyes on a problem project can be life saving.
keep your workspace clean.
If you have to have food or a drink nearby, use the rule of planes: always keep your work on a higher plane than anything that can spill or get knocked over.
And finally, the thing I need to do more often:
Work like the deadline is tomorrow morning,
until the deadline actually is tomorrow morning.