If I was caught shoplifting but charged with intent for burglary, how can get it brought down to a misdemeanor?

As an initial matter, you should probably consider getting an attorney as a felony is serious business in California and for that matter, any other state.

I am assuming that you are being charged with an attempt to commit California Penal Code Section 459, burglary. Under California law, burglary is the act of entering into a building with the intent of committing a felony within, whether that be theft or another crime.

Note: Remember this very specific language for later in this answer!

First, Section 459 is a wobbler, which means it can be charged as either a misdemeanor or a felony, depending on the circumstances. Your first approach may be to try to convince the D.A. that based on your (hopefully) clean record and the (hopefully) largely inane circumstances surrounding the crime in question, that a misdemeanor is in order. 

Even if you have a record and the crime itself was serious, this approach could be fruitful. On the other hand, it may not be successful even if, say, your record is squeaky clean and you are the future savior of the world. District attorneys, after all, are not always the most sympathetic folk - and they're often hired because of this quality.      

Second, you may try to get the charges dropped altogether. You can do this by showing at trial or before trial that based on the facts, you did not commit or could not have committed a burglary or a burglary attempt. To do this, you must establish that you did not have the intent to commit the crime PRIOR to entering the building. After all, the clear language requires that you formulated such a plan BEFORE going into the building - NOT once inside. It is often difficult for the D.A. to make a showing of such intent, especially if you have good facts to back your story up.     

There are other approaches, but these stand out as the first line of attack in most burglary cases. I suggest that you have an attorney evaluate the specific facts of your case for additional defense tactics. 

Good luck - And may the (legal) power be with you!