"SHould you wait till open to buy or can you buy at support before close and wait overnight to take advantage of the open?"
keep in mind if you do that the afternoon before an important economic report (you are checking the economic calendar on Briefing.com each and every day, right?) is released, as in this case, the eagerly anticipated non farm payrolls that the entire market is holding its bated breath for, than, a possibility is not that you will take advantage of the open, but the market might take advantage of you. Risk management is always paramount. Market may gap up and you will feel like a genius, and if it gaps down you will fell like a moron, especially if you are margined to the hilt.