The best thing to do is to ask to speak to an attorney right off the bat, before the field tests even start.
Agreed. However, doing that is somewhat of a challenge, as the LEO will most likely tell you that you don't have that right, because you are only being detained, not under arrest yet.
In fact, it may be best to refuse the field sobriety tests entirely. Some would argue that their only purpose is to provide evidence to convict you if you are below the legal presumptive BAC or BrAC level.