I've only ever had to hem mine (hint: use a heavy duty needle!), but have not tried to put in darts. If you want to avoid darts around the pockets, you'll want to try for the side seams - and the "right" way would be to take the waistband off, pick apart the side seams and re-sew those, and adjust the waistband to make it smaller.
I'm not sure I'd have the confidence to try doing that. Though I'm willing to hem, I figure I pay enough for a pair of jeans that they had better fit in the hips and waist. (And I refuse to buy expensive jeans if I have to hem them - only if it saves money will I hem.)