Begin by making sure each bolt on your bike is snug. Start at the front of the bike (handlebars, stem, and front brake), then work across the top to the rear (saddle, seatpost, and rear brake), and then down (derailleurs, crank bolts, and chainrings). Don't forget the bolts that attach your water bottle cages to the frame and your pedals. Your right pedal has a reverse thread, but you can tighten both by turning the threads toward the front of the bike.
If a bolt creaks or doesn't thread smoothly, back it out and apply a dab of grease to the threads before re-tightening it. To avoid overtightening your small bolts, hold your hex wrench near the head to ensure you don't have too much leverage.