The main rule, for a retail trader (other than possibly for a [I]very[/I] experienced, typically ex-institutional one with [U]very[/U] substantial capital) would be “Don’t have anything to do with it”.
Apologies if this sounds “negative”, but it’s completely realistic.
Even if you could ever manage to do it profitably (and it’s [I]hugely[/I] stacking the deck against yourself to try it), clearly no counterparty market-maker broker is going to tolerate a successful scalper for very long anyway, because the practicalities and speed of scalping predicate that it would be [B]them[/B] that you’d be scalping, not [B]the market[/B].
A genuine broker, for those with the funds to trade via one, has absolutely no problem with scalpers at all, of course, because scalpers trade far more frequently than anyone else (other than an automated HFT), and every trade represents a commission to them. Edited to add: this is also, of course, a substantial part of the reason why it’s such a misguided approach to trading in the first place, for aspiring retail traders.