We have all run into the "Attorney Who Cried Rush" at some point in time. There are many ways to handle this creature, some will work out well for you and some will not. Keep in mind that the longer you work for a particular attorney and the more you deliver the goods on time, the less the attorney will cry rush. Most of the time crying rush is simply the attorney's insecurity that 1) they will not have what he needs to be prepared or 2) you will not deliver quality work in time, compromising their reputation.
So here's what you do. First, from the your initial encounter with the attorney establish a rapport where you make the attorney feel comfortable with your ability to meet the deadline; Second, meet the deadline!
If you feel the attorney is crying rush and its really not a rush you need to have a conversation with the attorney where you ask for more details and ascertain exactly what the attorney wants, what he really needs and when he really needs it. By having this conversation you may be able to suggest an alternate plan that suits you both.
I can tell you that if you allow someone else to prioritize YOUR work you will be behind the eight ball all day, every day.
Most paralegals work for more than one attorney. Being able to prioritize your work to deliver to each attorney is your job. Keeping the lines of communication open will help both you and the attorney prioritize work, alleviate unnecessary stress and allow you both to do your jobs as efficiently and effectively as possible.
Sometimes its difficult to have this kind of conversation with a new attorney but you need to in order to keep your sanity. Just do it. But for the love of all things holy --- NEVER PROMISE ANYTHING YOU CAN'T DELIVER!
If you find that the assignment is going to take longer than you anticipated inform the attorney immediately and make sure you can suggest an alternate plan to get the project completed. An alternate plan could include - asking for help, altering the assignment, or maybe asking for an extension. Most attorneys are reasonable and will work with you. I have found that the attorneys who are completely unreasonable have a cadre of people that can work with them and do so well. Those completely unreasonable attorneys don't want to work with anyone except those that understand them. So you will rarely have to deal with them. But, if you do the same rules apply. Establish yourself as competent right from the start and deliver.