In my opinion the single biggest factor driving up clients' costs is organization. A client should have all relevant documents and evidence organized, scanned, and readily available. If email is an issue, such as in litigation or other large groups of documents, the more organized the better. If a client reviews all documents and prepares an outline, list, uses tabs, or otherwise provides an index of key documents, that can save the lawyer some time.
In addition to document organization, organization with respect to goals and needs is important. In litigation or in business transactions, when clients don’t know where they are going with a project or case, they can end up taking up more lawyer time.
Another common fee multiplier is a client that wants to micromanage a lawyer. This is something that the client is entitled to do. It is their business or their case, and if they want to discuss every little detail—every word in an agreement or legal document, spend hours discussing strategy, etc., they have a right to; but it can often more than triple a bill for a project. If you find an experienced attorney you trust, and you want to keep fees down, give them the big picture and let them do the best they can.
Finally, sometimes (or often) clients are not completely honest with the facts. This is not always intentional; often times the facts are skewed by their own bias. For example, there may be a relevant fact, document, or other evidence that hurts their case, but they just don’t see it that way, or perhaps subconsciously ignore that fact.
Yet it is much better – not just for fee issues – but for the client in its defense or prosecution of a case, if the lawyer knows everything up front. A client should be 100% honest with a lawyer from day one. It is much better for a lawyer to know about a bad fact up front so they have more time to figure out how to deal with it rather than find out about it after they have already implemented a litigation strategy. At that point, it might be too late to change or do anything about the bad evidence or fact. Therefore, even if the client is not sure if a bad fact is relevant, they should disclose it anyway. If they don’t, it not only could hurt their case, but end up driving up the cost of litigation, or even make the litigation a waste of time. For example, the lawyer’s entire analysis of the case may have been different, and the lawyer might have recommended a different course of action; e.g. settle, or perhaps not even go forward with a lawsuit.