The engine's runnin' but ain't nobody driving
Translation: Not overly-intelligent.

Tighter than bark on a tree
Translation: Not very generous.

Big hat, no cattle
Translation: All talk and no action.

We've howdied but we ain't shook yet
Translation: We've made a brief acquaintance, but not been formally introduced.

He thinks the sun come up just to hear him crow
Translation: He has a pretty high opinion of himself.

 As welcome as a skunk at a lawn party
Translation: (self-explanatory).

S/He's got tongue enough for 10 rows of teeth
Translation: Talks a lot.

It's so dry the trees are bribin' the dogs
Translation: We really could use a little rain around here

 Just because a chicken has wings don't mean it can fly
Translation: Appearances can be deceptive.

This ain't my first rodeo
Translation: I've been around awhile.

He looks like the dog's been keepin' him under the porch
Translation: Not the most handsome of men.

They ate supper before they said grace
Translation: Living in sin.

As full of wind as a corn-eating horse
Translation: Rather prone to boasting.

You can put your boots in the oven, but that don't make 'em biscuits
Translation: You can say whatever you want about something, but that doesn't change what it is.