Hi there, a rule of thumb that I learned was that in order to get information you have to give some!!
For instance, "who what where and when" would be good guidelines to fill out a request for information. Say you are looking for Jacob Anderson, that would be who, a grandfather, great grandfather etc would answer what relationship he or she would have to you the searcher or to the person your looking for. Where would be a country, a region, in the US a state, a county etc. When would be like.. during the migration of the Irish immigrants to the US or Canada the Anderson family came over in 1722 ... or say the person was in a particular war, and served in the military so you would add, during WW1 Jacob was a private in the British Army.
Hope that gives you an idea of what would help us find someone your looking for or what information is out there about someone. Volunteer genealoglists can use what you provide to search census reports, military records, travel records etc.