Commission is the cut a validator takes from your rewards before passing the rest to you, typically 0-15%. A lower commission isn't automatically better if it comes from a validator with poor uptime — missed blocks cost you more in forgone rewards than a slightly higher commission would.
Uptime and slashing history matter more than headline commission. Most block explorers and staking dashboards publish a validator's historical uptime percentage and whether it has ever been slashed. A validator with a long, clean track record is generally a safer delegation target than a brand-new one offering an introductory low commission.
Decentralization is worth weighing too: delegating to whichever validator is already largest reinforces stake concentration, which weakens the network's censorship resistance over the long run. Many stakers deliberately choose mid-sized, reliable validators instead of the top one or two by stake.
Finally, check whether the validator or pool has a minimum delegation amount, how often it distributes rewards, and — for liquid staking protocols — how the underlying validator set is selected and monitored, since that's ultimately where your risk sits.