Treat them according to standard rules of accenting. There are exceptions (especially with -facio, as in "-fis"/"fit"), but my advice is to ignore them for now, if that doesn't offend you. It's a matter of dispute, in any case.
Omnia verba eodem modo tractes. Sunt exceptiones (praesertim cum "fis"/"fit" composita) quae, tuâ veniâ, a te concessandae sunt, ut opinor. Res obiter est quae in controversiam adduci potest.
I'm writing in Latin hoping for correction, and not because I'm confident in how I express myself. Latinè scribo ut ab omnibus corrigar, non quod confidenter me exprimam.