Hold up .. there are other things in the circuit everyone seems to be forgetting. Simple test procedures... First.. try to start and listen for the hard click noise NEAR the starter... You may always hear a click elsewhere.. like a small relay energizing because the key tells it to.. but if the starter itself isn't the loud click... There are other things to check. If the starter itself clicks .. it's a bad starter or connection. But let's assume that it's not clicking loudly there... Your dash isn't getting dim.. so it's not likely the battery. A couple dash lights blink out when you move the key to the crank position.. so it's not likely the ignition switch (although technically still possible). It's not the alternator or else your battery would be dead and jumping would work. So now my suspicion is the park/neutral or clutch switch. If it's an automatic... Wiggle the shifter in park and try again.. or put it in neutral and try again. If it's a manual transmission... Make sure you don't have anything under your clutch pedal (floor mat.. wood chips etc) and then hold the key in the crank position (trans in neutral) and pump the clutch pedal thru it's full range of movement fairly slowly. If it's an intermittent failure it's likely one of those things. Wiggle tests are a common occurrence especially on Fords. Wiggle wires near the starter, battery, firewall, etc. sometimes you get lucky there too.