From the bottom, there are two "basic" ideas and endless variations on that theme.
either keep the guy in close so that he has no room to strike with authority, OR, use the guard to keep him at a distance.
I use my forearms and shins to block punches, which then directly translates into wrist control. It feeds my open guard, which I use to attack.
If he does get space, start slipping with your upper body while moving your hips as hard as you can to get him off balance--forwards, backwards, etc.
"In the world of martial arts, respect is often a given. In the real world, it must be earned."
"A stupid man's report of what a clever man says is never accurate because he unconsciously translates what he hears into something he can understand. "--Bertrand Russell
"Liberals - Cosmopolitan critics, men who are the friends of every country save their own. "--Benjamin Disraeli
"A conservative government is an organised hypocrisy."--Benjamin Disraeli