Just as important as ordering things, can be limiting things. Putting a LIMIT on your SOQL statements let you specify the maximum number of records to return.

To grab any 4 Opportunities that are not closed we query like we normally would, and apply the LIMIT at the end.

SELECT Name, StageName
FROM Opportunity 
WHERE IsClosed = false
LIMIT 4

Same is the case when we add order to things. We apply it all before we start to LIMIT things down. To find a single opportunity in review with the highest probability we first order, and then limit.

SELECT Name, StageName, Probability
FROM Opportunity 
WHERE StageName = 'Negotiation/Review' 
ORDER BY Probability DESC
LIMIT 1