I do combat by the book ... exceptDo you run everything by the book, do you cut corners, or even outright ignore certain aspects? Do you otherwise add more precision with variant/house rules?
Consider the question from the separate points of view of being precise on the following:
1- creature positions and movement (e.g. TotM vs battlemat, step-by-step movement around obstacles, counting diagonals x1.5)
2- distances and weapon/spell ranges (e.g. measuring exact ranges vs ballparking near/far)
3- elevation, angles and directions (e.g. adjudicating cover carefully from different directions)
4- terrain and obstacles (e.g. ignoring vs taking small objects on the ground into account, like a chair)
5- lesser actions on someone's turn (e.g. handwaving/enforcing object interaction rules, switching an object between hands)
6- spells somatic/material components (e.g. checking against free/occupied hands)
7- light sources and visibility (e.g. keeping track of exact areas of bright light, dim light, darkness)
8- any particular tactical area (e.g. hiding in combat, flanking, facing)
• I encourage stunts, and adjudicate them narratively or by skill checks, ... which actually is by the book!
• I ballpark ranges to 10 feet, 30 feet, 100 feet, 300 feet, 1000 feet. So normally, melee, close (30 feet), or "distant".
• I ignore illumination. Especially indoors, everywhere is "bright", "dim" partially obscured, or "dark" /totally obscured.