Hi Malaika,
I require all new hourly clients to pay a $XXX deposit when they sign their contract. The deposit is held against six months of regularly paid invoices. That way, if something should happen and they default on a payment, I'm covered at least to some degree. It hasn't happened to me in a *long* time (thank goodness) because I've gotten very picky about who I work with but the deposit has saved me having to chase down money owed on at least twice.
After the client has built up good credit with me by paying their invoices on time and in full I return the deposit to them (usually by applying it to the current invoice at that time).
At that point there is a relationship established and I don't worry about taking a deposit unless the client requests a substantial project.
I hope this info helps!