Writing good English is one of the key measurements for RA and TA appointments. Among others finding financial support for your graduate school depends upon your discipline and research grants made available by the NSF and the government organizations like Department of Energy, Department of Defense, Department of Agriculture and so on. Before you apply look into the departmental past and current research works and figure out who is securing grants to conduct research. Message me with your specific concern and I might be able to pull out some good information for you. (intellectual_suicide@hotmail.com).