playing trills

What would be the best way to play teh following with alternate picking?
Iron Maiden - Phantom of the opera
(intro)
e-------15 ---12-----
b------------------12
repeat a few times

or stairyway solo
e-------------20--17----
b---------------------17

should i bar the last two notes? if so then it sounds like i'm strumming the two ...
neeed help.

I would bar them. Of course muting is very important here.

The "Stairway" example that you give is played by picking the 20th/1, pulling off to the 17th/1 and picking the 17th/2, usally this is a repeating lick, probably one of the most used licks in Rock music.... I haven't heard the Iron Maiden song, but from what I have heard of their early stuff, it's the same lick..................

Yes, you should bar the last 2 notes.

You can mute by 2 methods:

1-removing your fretting hand's index slightly off the e-string to mute it.

2-by one of your picking hand's free fingers (Usualy the pick is held between thumb & index , so you have 3 fingers free for muting purposes).