I do it pretty much as I did when with the airlines- check current and forecasted wx at departure and destination, winds aloft. Area forecasts, turbulence reports, iceing reports, alternate wx- depending on the wx. Never used "flight computers" except on private, commercial, and instrument written and certificate flight exam. ATP was done with the company.
Typical back then was: into dispatch, coffee, greet whoever there I knew, make 1 or 2 personal phone calls. Sometime during that F/O says something like "CAVU everywhere." My mind says "xx 1/2 hrs, xx,xxx lbs fuel." Probably take a look at the millibar charts- gives winds and idea of turbulence. F/O or dispatcher shows me the papers, all figures reasonable, sign the release. Grab my flight bag/suitcase, get into the terminal, look important as the little kids, women, and whoever else look at me in awe.
Get into my seat. "Sir, we got SID blah blah blah departure, I put blah blah on your set, departing 27left, 32right. Secondary fuel pump N0.1 intermittent."