How do I manage combat situations without a physical map?

I am about to start running a new DnD campaign and for the first time in a long time I am running it at a table with pencil and paper, in recent years players have had there own laptops at the table, and I have run using roll20.

Prior to using online resources I ran my combat systems pretty free not worrying to much about movement speeds or displaying things out on a map but having now got used to players moving on the roll20 map I find that I missed an important aspect of combat.

The session this week is a one shot and in the medium term I have plans to order gridded paper and draw out my combat maps, and possibly look at getting some miniatures, what is the best way to manage tings like Player/NPC Monster positions without a physical gridded map or miniatures