Knowledge is Power
Regardless of whether you are on probation or in pretrial proceedings, failing to appear will usually result in bench warrant. The first thing to do, then, is to call the court and find out what the bond amount is. Try to find out what the court's policy is regarding walk-in arraignments. It would help if an attorney got involved to facilitate the surrender.
Most judges, in my experience, would prefer that you come in and explain why you can't pay your fines and costs than see a petition for a bench warrant. Likewise, probation officers or more inclined to work with you if circumstances prevent completing community service obligations or 12-Step meeting attendance. If you've already failed to appear, make every effort to clear up those outstanding obligations. Again, a lawyer can help present your case, your efforts, and your obstacles quickly and in a language the courts can understand.
At the Courthouse: Now What?
Coming in under your own power is a good first step. For a first violation, in many instances "intermediate sanctions" short of jail are the rule. These might include additional work program days, community service, fines, or extending probation. Remember who's order has been violated: the greater the violation and the smaller the respect for the judge, the higher the chance of incarceration. The key with most judges is truly working a program and bettering yourself.
What to Expect from Your Lawyer
If you are able to retain an attorney, you should expect that he or she will be making all appearances personally. With your consent, the lawyer may send a fully-briefed associate. Of course, the lawyer's staff will also be involved with certain tasks, but your lawyer needs to be in court, on your side. For most probation violation cases, expect your attorney to spend about an hour in conferences, telephone calls and research. Time in court may take an hour or a day, depending on the judge. Every case is different, and yours may require more or less time depending on the complexity of the issues and other circumstances.