Your kitchen tap gets heavy use every day. Swivelling the head from side to side and other normal actions can loosen the tap if it's not properly fastened, causing the unit to shift around on the edge of the sink. Tightening kitchen taps often takes two people simply because it is difficult to reach the fasteners while holding the tap steady at the same time. To keep your tap tight once it is fastened, you may be able to add an adhesive to the fastener threads or install a locking washer above the nut.
Remove any items from under your kitchen sink so you have complete access to the plumbing.
Position your upper body beneath the sink so you can look up behind the sink bowls to where the tap attaches.
Shine a torch at the tap connections and determine how it is attached to the sink. There may be one bolt beneath the spout itself, two bolts on either side of the spout, or nuts that tighten around the entry holes for the water lines and spray hose. The bolts may be traditional, threaded metal or short, relatively flat plastic, or a combination of both.
Ask a helper to position the tap and hold it in place from above the sink.
Turn any nuts or connectors clockwise to tighten them. Hand-tighten plastic or wing-nut connections, or use a adjustable crescent wrench to tighten metal nuts. Special wrenches that fit into tight spaces are often available at hardware shops.
Ask your helper to wiggle the tap. If he is able to do so, tighten the nuts further or look for a nut you may have missed. Repeat until your tap is secure.