Lift up a section near the crown of your hair, and use a rat tail comb to tease or backcomb the section underneath it so that it essentially becomes frizzy & gives it volume. Give it a good mist of strong hold hairspray, then smooth the front layers over the teased hair. Gather in the back forming the bump and pin into place. Mist again with hairspray to fix your bump into place.
Now if you are short on time then you may find it difficult to achieve the perfect bump. Or maybe I'm just not talented enough with my hair. :) Anyway, maybe you considered buying Bump Its which are found either online or at your local store (Walmart, CVS, Walgreens, etc.). Bump Its can cost you around $9.99 (unless you buy online), which is fairly cheap. HOWEVER, I stumbled upon the Dollar Tree version today, so I bought it to try out and I came to the conclusion that my $1 version works just as well! So if you are wanting to try Bump Its out, I suggest you stop by your local Dollar Tree & buy the High on Hair.