1) Have a story you really want to tell.
2) Let that story brew in your head until it drives you crazy and you HAVE to put it to paper.
3) Put it to paper.
4) Put it on a shelf for a year.
5) Pull it back off the shelf and revise it with the 40+ changes you've been carrying in your head for a year.
6) Invite actors to your intervention, aka First Reading.
7) Put it back on a shelf for a year.
8) Have a nervous breakdown, have surgery, and get thrown into medically-induced menopause (this may be difficult for male filmmakers).
9) Pull it back off the shelf and start asking yourself, "Can I?" and "Should I?" Rinse. Repeat. "Can I?" "Should I?"
10) Continue asking those questions for at least another year.
11) Quietly start putting together cast, crew, locations, music, budgets, licenses, equipment, air transportation, housing, shooting schedules, insurance, company legal formations, sets, costumes, flying rigging, etc. Don't tell anyone, just in case you decide to quit.
12) Send your screenplay to a few friends who won't tell anyone if it sucks.
13) Quit on a daily basis, because everything appears to be falling into place WAY too easily.
14) Lock down two weeks for shooting and put the wheels in motion.
15) Go on vacation 2 months prior to principal photography, because that will test the waters.
16) When lead actress pulls out while you're on vacation, do NOT panic. Just call your friends and get a better actress!
17) Revisit your overall budget. Make it a daily budget, so that you can see how much money you will lose at any point during principal photography if you cancel the project.
18) Two days before principal photography starts, send the screenplay to ONE MORE PERSON, just to be sure you really should do this.
19) The night before the first day of shooting, consider calling everyone to tell them it's off.
20) Arrive at the first day of principal photography, knowing that about 300 pieces of the puzzle HAVE to pull together over the next two weeks or you're screwed. But find peace in knowing that you have your daily budget and know how much money you will lose whenever you finally decide to quit.
21) Once it starts, have someone take pictures and video, because it will all be a blur and you will remember very little of the next two weeks.
22) When principal photography is completed, take a deep breath and relax... for about 10 minutes, because NOW the hard part begins: post-production, including music.
23) Spend 7 months editing every night. Watch rough cut after rough cut after rough cut, because every change you make (even small) will alter the pacing.
24) And when it's done... and you're uploading your 118 minute movie to IMDb and Withoutabox... write down what you've accomplished. Because you will have forgotten that your ultimate goal in the beginning was simply to write a story for your son to read when he got older.
And thank ALL your friends and family who have held you up during the whole process... who have shared their talents with you... who believe in you... and who never hesitated to be blatantly honest. Because those people have just made your story worth sharing... :)