I use a firesteel (LMF brand) as my primary firestarter and have found that, in conjunction with PJ cotton balls, is a very simple way to get a fire going.

I think all the key points that I've found helpful through trial & error have been mentioned here, but they are:

• Keep the striker stationary & then pull the firesteel towards yourself. Before moving to this method I was forever knocking my carefully arranged tinder and kindling all over the place.
• Using the PJ cotton balls, pull the fibres apart & fluff up the ball ... also ensure there isn't too much PJ which will cause them not to take a spark (something I found out when I tried dipping the cotton balls in melted petroleum jelly ... I ended up with thoroughly saturated balls that would burn longer, but couldn't be lit with a spark)
• Using natural tinder, make sure it is very dry!

On that last point, I haven't got much experience yet using natural tinder exclusively, but one experience really showed me the difference between dry & kinda-dry tinder.

On one trip I decided to try making a fire from 100% collected materials, so we gathered up some wood & I found some Old Man's Beard to use for tinder - this was in the late afternoon on a fairly warm day. Everything went great, the Old Man's Beard took the spark easily and the fire was a success. The next morning I get up and decide to try the same thing. This time however, I simply could not get the Old Man's Beard to stay caught. After a while I gave up, pulled out the PJ cotton balls and got the fire going with some effort. See, the difference was everything was ever-so-slightly damp in the morning which hampered my firestarting efforts.

My big take-away from this was that if I wanted to use natural tinder, I should be collecting it and keeping it in my pocket or something to keep it dry rather than trying to simply collect it when I needed it.