Typically no.1 will be the best contact/on-base/speed combination, no.2 will be a strong hitter somewhere in between that ^ and power, then no.3 the best power hitter, no.4 the next best. Normally the 2nd best contact/on-base/speed guy I’ll put 9th, to be on for the top of the lineup, unless there’s a serious quality drop with the no.5-8 batters. That’s with a DH, anyway. No-DH I tend to keep the pitcher 9th, but I need to read up on that more
(So basically, I want guys on-base fairly often for the ‘best’ hitters, and theoretically they have the space to use their speed.)