I've only taught myself through trial and error over the last few years of having swapped from the older Schrader (or 'car' type) valve to the now more common Presta. This has also been compounded by me having had a few cheap and nasty pumps with absolutely useless valve heads on them.

If you're getting used to a new pump, or not used to using it on a presta valve take a moment to have a look at the head of it, and how it sits on the valve stem head. Operate the little clamp lever whilst looking into the valve head. It may be harder to notice on some pumps than others - but in one of the clamp positions the rubber grommet within it should constrict tighter. Take note which clamp position is 'loose' and which is 'tight'. Most of mine have been 'loose' parallel to the pump hose, and 'tight' perpendicular to the hose.

If you've been using your same pump on a schrader valve on another bike, or some other pneumatic tyre around the house it's probably not going to work as is straight away on the presta unit. there's a good 2 or 3 mm difference in the valve stem diameter and the schrader heads won't clamp and seal onto the presta stem. Speaking through the half or dozen or so floor & mini-pumps I've owned in about as many years - most heads have a flippable grommet in them that has a different diameter hole at either end allowing it to be used on either sort - with a little bit of fiddly swapping around. You have to often unscrew a little head piece to reveal the grommet - and they can be a cow to get out; especially being careful not to damage it to flip them around

Having said this - I have owned absolutley **** quality pumps that have worked for a little while - but the rubber has perished just enough to never get a proper seal again causing me no end of grief until I tried another pump. If through repeated tries with your own pump you still have no luck - borrow a friends or take it to your LBS to try with one of theirs and get them to show you.



But assuming you're confident you have the right pump head configuration and it will seal; the general steps are

1) remove the presta dust cap; usually black.

2) back the little thumb nut off on the end of the valve. Think of this of a little wedge that when under pressure stops the valve being pushed in and inadvertently letting air out.

3) ensure the pump head clamp lever in the 'loose' position. on my good Serfas floor pump I also back off the little retainer nut that holds in the pump head grommet a little bit. this is just to allow the head to get further on the stem

4) Quickly place the head over the stem - expect a little bit of air to come out as the valve is pushed in. Quickly flip the head lever to the 'tight' position and also re-tighten the head grommet retainer to ensure a good seal.

5) Start to pump! Depending on how much air is still in the tube you mighn't feel the resistance of pressure straight away. If the pump head isn't sealed properly against the valve stem you will hear air escaping around it; Double check your pump and return to step 1). If you get a quite sharp pressure resistance straight away - and that doesn't correlate as to what's in the tyre - the valve in the stem mightn't be opened properly, or your pump head isn't sitting properly. Return to step 1) and recheck.

6) Assuming your pump has a guage you should see your pressure steadily increasing. Be mindful of what maximum pressure your tubes and tyre are rated for. This should be printed somewhere on the tyre sidewall. After a while you often get to know by feel if you don't have a guage. compare it to the other wheel - assuming that's about right itself.

7) Once the pressure is right get ready to remove the head; loosen the little grommet retainer just slightly and quickly flip the pump head lever to 'loose' and remove. Again there's probably be an instant of air loss as the valve recloses but it should be only for a split second.

8) tighten the little brass thumb nut in the valve stem with your thumb & index finger and replace the dust cover. Voila! Ride on, dude!

Apologies if any of my terminology is confusing or contradictory... or if this reply is overkill - but hopefully amongst all my noise there'll be at least one pointer to see you right.