I think it is a good idea to get a teacher=)
There are lots of ways to build up strenght and speed. pullon/pulloffs for example in scales up and down fast will train you finger muscles, speasially if you use heavyer strings like 011(i always use 010, and i don't play slower because of that)
I like to practice fast guitarsolos on my acoustic guitar with 012 strings. when you play it again on electric ut is
much easyer=D
And practising with metronome is a good idea ofc.
practicing a scale with 1-2-3-4
1-2-3-4 is pointless in my opinion, because you would never use that scale in any song. practice a scale that you could use for something instead. there are the blues scale i wrote above and many others. i practiced this alot:
--10-9--7-------------------------------------------------
------------10-8-7--------------------------------------
---------------------9-7-6------------------------------
--------------------------------9-7---------------------
---------------------------------------10-9-7-----------
------------------------------------------------10-9-7---
To play alternate picking, use only you wrist. do not move your arm. relax your arm, and ofcourse hit the strings up and down.
By the way,
I have played guitar for some years now, but i resently bought a powerball (
http://www.powerballs.com ) ^^
i have not noticed any special improvement in my guitar playing because of it, anyway it's supposed to train finger, wrist and other muscles in you arm. when you get it spinning at 15000 rotations per minute it gives many kilos of force as much as 15 i think.
Anyway, it is very fun and addictive. I higly reccomend it!