Avoid that dangling modifier!

Examples:

Dangling Modifiers (Purdue OWL)
Misplaced Modifiers (Darling On-Line Guide)
Keep related words together. (Strunk and White)

Modifer Placement (Darling et al)
Modifier Placement II (Darling et al)

Avoid sentence fragments! A sentence fragment may have both a subject and a verb, but it must express a complete idea to be a complete sentence.

Example:

This clause contains both a subject and a verb, but it does not express a complete idea. (It is a adverb clause.)

Sentence Fragments (Darling et al)
Sentence Fragments (Purdue)

Sentence Fragment Exercise 1 (Purdue)
Sentence Fragment Exercise 2 (Purdue)
Sentence Fragment Exercise 3 (Purdue)
Repairing Sentence Fragments (Darling et al)
Fragments and Run-On Sentences (Darling et al)
Fragments & Types of Sentences (Darling et al)

When you revise, take the time to make your sentences clear and elegant. Use parallel forms for parallel ideas.  

Example:

Biblical Passages in Parallel (Darling et al)
Abraham Lincoln's Gettysburg Address (Darling et al)

Express Coordinate Ideas in Similar Form. (Strunk and White)
Parallelism (Darling et al)
Parallelism (Purdue)

Parallel Structures (Darling et al) 
Parallel Structures 2 (Darling et al)