i used to have the same kind of problem with you. if you're in
exam situation and all you need is a rough shape of the graph, just
substitute in values ranging from say x=-3 to 3.
For eg. if y=x^2,
when x=-3, y=9
x=-2, y=4..
and so on and so forth. then just plot a rough graph.
if you're at home and you have no math programme to help u draw
a graph(mathematica) and such, just use microsoft excel.it works
just as well if you don't need especially perfect and precise
graphs. =) hope i helped