The answer is: correct comma splices, increase sentence lengths and correct fragments.
A comma splice is a wrong separation between two main clauses by using a comma. For example:
"If you are interested, please respond to this e-mail to sign up - only 40 spaces are available."
Sentences could be improved by increasing their length. For instance, the next two sentences could be joined using a comma.
"The workshop will take place November 10 and 11, from 9:30 a.m. to 5:30 p.m."
Finally, sentence fragments are groups of words that do not indicate complete thoughts. To become sentences, they need to have an independent clause with a subject and a verb, so that it can stand on its own. For example, the fragment "Led by Joseph Pelletier" could join the previous independent clause:
"The Human Resources department is happy to announce a career development workshop, which is led by Joseph Pelletier."