This is not gospel - what works for one person doesn't work for someone else, and we each form our own style. Please take these suggestions in that light.
Feedback is always welcome.
It's when things go awry that it gets stickier. If they arrive a few minutes after the start, and it makes the number of players odd, then you might consider giving them a bye round. If the number is even, then see if the player on the bye round would pair with them - it makes for a shorter game, but is possibly better than sitting around. Anyone arriving after round 1 has finished is probably out of luck. It's often difficult to gauge when a player is stalling as different players have different speeds, and what's slow to one is normal to another.