Set your lawnmower to its highest height setting. This will help your mower go through the tall grass easier.
Mow the lawn when the grass is dry. Wet grass is more difficult to cut, and has a tendency to gum up your lawnmower.
Mow the grass once with your lawnmower on the highest height setting, then mow it again two to three days later at a lower setting. This will help prevent damage to your lawn.
Mow only narrow strips of grass, between 6 and 12 inches at a time. This will help prevent the grass from gumming up your mower.
Move slowly when you are mowing. Doing so will cause less grass to be cut at a time, and will help prevent your mower from being overwhelmed.