(Yes, Part 1 was a long time ago. But that doesn't mean that this can't be a continuing series.)
I wish my clients knew that saying "it's not my m.o." is not a defense.
Sometimes a client with a long rapsheet will tell you, "Look at my rap sheet, that's not my m.o." We all know that drug possession and shoplifting go hand in hand. I mean, think about it, if I can't afford my $3-a-day Starbucks habit, where's my client getting the money for his $50-a-day drug habit? But, for example, a client who is constantly arrested for drug possession will be arrested for shoplifting. The client will eventually say, "But check my rap sheet. Yeah, I got a drug problem, but I don't shoplift. That's not my m.o." Oh, why didn't you say so? I'll tell them to just let you go.
Just because you've never been arrested for this particular charge before, it doesn't mean you can never be charged with it ever. There's a first time for everything. Add to that the fact that you've already been convicted of a number of crimes (thereby stigmatizing you as a criminal, even if it's not "that type of criminal"), and you can see that "it's not my m.o." isn't very convincing.
Further, I'm sorry to throw this in there, but... you don't really have the definition of m.o. figured out. Generally an "m.o." is much more detailed than "you've been charged with that crime before." It's more of a signature or a very distinctive way of committing the crime that may be used to identify you later. So, for example, "robbing banks" isn't an m.o. It's just a crime. Robbing banks while wearing a cheerleader uniform and Nixon mask might be an m.o. Even something like robbing banks on the 15th of the month right before closing time might be an m.o. An m.o. can later be used to identify a criminal. So, if you're arrested robbing a bank wearing the cheerleader uniform and Nixon mask, it's a bad thing if the police figure out your m.o. because they'll tie all of the other cheerleader/Nixon robberies to you. What you need to know here, though, is that m.o. does not mean preferred crime or crime you've been caught doing most often.
Finally, I just wish my clients knew... that going to the judge and saying, "But, Your Honor, my client would like the court to know that he does not steal cars, he only shoplifts," is NOT going to help at all.
The definition of modus operandi (or "m.o.") can be found here on law.com.