writng intros and riffs are easier than some of you beginners would've ever imagined.
sometimes it is about just muckin' round with the settings of the amp, and fiddling round with the guitar.
but sometimes, other, more serious players, actually take the time to sit down construct an intro or riff.
to write a riff, it should be no more than two bars long if you have repeats, otherwise it should go no longer than four bars, otherwise you would lose the interest of the listener.
it should have power chords, and lots of them,, if you're only a beginner, because that will make it a lot easier to write.
for an intro, you could use a riff that you just created, OR, you could create something completely differnt, from single strings and others. try and use double-stops, i use them a lot.
here is a riff i cooked up a while ago:
e----------------------------------------
b----------------------------------------
g--9-9-9--7-7-7--5-5-5--3-3-3-3--
d--9-9-9--7-7-7--5-5-5--3-3-3-3-- try starting your riff with this, on any two
a---------------------------------------- strings, and add as much or as little more as
e----------------------------------------
you want.
as the songwriter and the lead guitarist for the band Ice On Fire, i suggest you take my advice.