#1
I can come up with some pretty good riffs and stuff on guitar(playing for about 3 and a half years) and have some experience with theory but my question with the way a song is set up.. I'm kind of starting to write , any help?
#2
Thats a pretty huge question as there are dozens of musical forms and really you can do anything you want. It also depends on what type of music you are trying to write

I'll lay down some basics for you though...

A=verse
B=chorus
C=bridge

try starting with ABABA or something similar

than maybe try ABABAAB

Than try ABABCB

You can really do anything you want to, plenty of songs are all verse and that is fine

All of the verses (A) should follow a simmilar or identical structure, same with the choruses (B) and the chorus should also contain the lines that your song revolves around. the bridge is kinda like the chance to mix things up.

verses develop the story
choruses tie it together
and bridges well they make it more interesting to listen to
#3
First of al you begin with writing the words.
Ok when you are finished you divide the song in
- Beginpart
- Bridge
- Verse (must take longer time)
mabe some other time also a solopart.

When you divided the song you'll try to find a good melodie for you song.
There are not no rules except the scales, but the begin chord of your song is important. I will help you for scales. Check this out:

The major scale of a note concists of 7 notes: 1.Do 2.Re 3.Mi 4.Fa 5.Sol 6.La 7.Ti
Lets look at the A-major key: A - B - C# - D - E - F# - G#
You can see that in A-major scale A=do, B=Re, C#=Mi...,G#=Ti

Now we find out what we can do with this information. For playing chord IN THE SCALE there is the next rule:

Do=major, Re=minor, Mi=minor, Fa=major, Sol=major, La=minor and Ti=(no chord).

Possible chords :

Do : { 6, sus2, sus4, maj7, maj9, }
Re : { sus2, m7, 7sus4, m9}
Mi : {m7, 7sus4, sus2}
Fa : {6, maj7, 9, dim, sus2, maj9}
Sol : {7, sus4, 6, dim, 9, sus2}
La : {m7, sus2, sus4}

Start always in Do and sometimes starting with Fa for a part would be nice.
Never end in Do (it ckicks your ass kid) and be becarefull for Re. I end in mi sus2.

A - B - C# - D - E - F# - G#
A#
B
C
C#
D
D#
E
F
F#
G
G#

Never sing for the devil, sing for God and goodness.
#4
A lot of good songs are;

Intro
Verse
Verse
Chorus
Verse
Chorus
Bridge
Chorus
Chorus


But obviously nobody is saying you HAVE to do that.