Not hard and fast “rules”, but what I’ve done in every soulslike so far is:

• Melee only, not even ranged weapons to pull enemies, either I lure them via spacing or I deal with the group.
• No spells, not even any utility spells.
• No consumable soul items. I tend to naturally hoard anyway, and this prevents me from getting overlevelled while exploring thoroughly.
• No multiplayer or summons, I prefer to learn bosses solo and get the full experience.
• Try to beat every boss available.
• No guides, ofc, although I discuss the game with my friends in discord, and they help me not miss any particularly easy-to-miss bosses. They’ll let me fail NPC questlines and such organically though, as they should.
• I also pretty much always end up with the biggest bonk I can find, but that’s not a rule, just my preferred playstyle lol.

Have played through pretty much every From Soft Soulslike this way, and this is just the playstyle I organically gravitated to for my first playthroughs. Has been the most fun for me, personally.