One common error in this area, especially among those trying to write fast, is ending up with run-on sentences, two or more complete statements put next to each other without proper punctuation between them.  This is typically an error that a grammar software can easily handle, although some cases may prove trickier than others.

The sentence “I bought a new computer this morning it broke immediately after that” is a good example of a run-on sentence, consisting of two complete sentences put side by side without anything to separate them.  You can fix it easily by doing one of three things, either by:

• adding a period, as in “I bought a new computer this morning.  It broke immediately after that.”
• adding a comma and a conjunction, as in “I bought a new computer this morning, but it broke immediately after that.”
• adding a semicolon, as in “I bought a new computer this morning; it broke immediately after that.”

Run-on sentences can be tricky in a few situations that might lead to leaving them overlooked.  As such, you’ll need to take some extra vigilance in order to catch them when they occur.  As a rule, always pay close attention to the following situations:

• When the second sentence involves a transitional word (e.g. as such, however).
• When the second sentence gives directions based on a subject on the first sentence.
• When the second sentence includes a pronoun that refers to the same subject as the first.