Don't ruin your client's weekend by getting him arrested on the wrong day
Let's say your client needs to make contact with the authorities (maybe he needs to check on a warrant) and there's a chance he could be taken into custody. Don't let him do this on a Friday.
In general, people who are arrested must be brought before a magistrate within twenty-four hours, but that time period does not include weekends. Jurisdictions vary, but make sure your client won't have to spend the weekend in jail waiting for the magistrate to set bail on Monday.
Don't ruin your client's future by failing to advise him of consequences
Before you let a client plead, make sure he knows everything he's giving up. A criminal conviction can affect his social security benefits, voting rights and gun rights. If your client is a teacher, he could lose his teaching credential by pleading to certain offenses. Know every implication of a plea in your jurisdiction and advise your client accordingly.
Don't ruin your client's life by letting him take a bad plea bargain
Of course, it's up to a client whether to plead guilty or not, but he will be heavily influenced by your advice and attitude. Don't give up and let him plead guilty just because wants the case over with (or because you do). And never let him plead without an agreed-upon sentence.
Even if the facts seem overwhelming, many things can happen if you just give it time. You might dig up the fact that the prosecutor's main witness lacks credibility because he's a convicted felon. The police might fail to show up so many times that you convince the judge to dismiss the case. You could win a motion. The prosecutor could get so sick of seeing your face he offers you a great deal. (I've had all those things happen.) So wait until you get a reasonable settlement offer, one that's better than what your client would get if he goes to trial and loses.
You are your client's hero
Sometimes the facts are just too strong, and a client ends up with a harsh sentence. When that happens, let him at least be comforted by knowing that there was one person who fought for him, advised him well and never gave up.