1) Length
The golden rule is group similar ideas together. It’s a bit different in online writing. It may go something like this: Group your similar ideas together but leave the most striking ideas on their own. Split as many sentences as your good sense allows you.
For example:
When Wenger signed him for a record fee in 2013, the question was: What were they thinking in Madrid? The question still stands today.
Ozil has been a gold mine for internet memes. Assister, pre-assister, call centre operator: all because of his exquisite ability to free his teammates with the killer pass.
This is good enough: it is not a big chunk of text. But it can better:
When Wenger signed him for a record fee in 2013, the question was: What were they thinking in Madrid?
The question still stands today.
Ozil has been a gold mine for internet memes. Assister, pre-assister, call centre operator: all because of his exquisite ability to free his teammates with the killer pass.
The sentence that stands out asks the reader: Why does still stand today? And the answer is because Ozil is just as good if not better today. The lone sentence strikes a punch, grabs the reader by his lapel and shakes him: Hey, are you awake?
Use these low shots from time to time. It brings life to the article.
A rule of thumb is if a sentence asks the reader a question without asking it, it can be split off from the paragraph.
2) Ending it
Pay extra attention to your last sentence in a paragraph. It is the logical bridge to the next paragraph so it should pack a punch. If not, consider using a transitory phase in the next paragraph.
For example:
Chelsea’s current team possesses the best defensive unit in the Premier League, a midfield packed with skill, speed, guile, tenacity and the most lethal centre forward in England in Diego Costa. They are the ultimate Premier League predator and can beat teams in a multitude of fashions.
What multitude of fashions? The sentence is not striking enough to have a place on its own but asks a question which is answered in the following paragraph. It is the bridge which invites the reader to proceed and find out.