Is there a proper way to fill an electrical panel?

The main thing is to watch your stab limits. Breakers clip on to panel parts called "bus stabs". They have a practical current limit, often stated on the panel label.

Some people get it in their head "put the biggest breakers up top" (as if to reduce the few inches current must flow down the bus, as if that matters). Then they fit a 100A breaker opposite a 50A breaker, and voilà, they have put 150A on the bus stabs in the first two rows.

Also beware of "double-stuffing" panels - lots of people get the 'bright' idea to save themselves the cost of a pizza by getting the smallest panel they can. Then they either choose from the outset, or are forced into later, going with "double-stuff" breakers that put 2 breakers effectively in 1 space (or 2 240V breakers in 2 spaces). I recently saw a setup that had a 40/40 quadplex across from a 30 2-pole. The person wanted to double-stuff the 30 to a 30/50 to feed a subpanel. Notice a problem? You now have an 80A (40/40) breaker across from an 80A (30/50) breaker. Stab limits again!

Go big. Go really big. Spaces are cheap. Regrets are expensive.