How should i approach my song composition.for eg what chord progression should i select,inspiration,and other aspects.I am a singer and guitarist and want to compose songs on guitar.
I would advise you to start drinking heavily.
I wouldn't bother with inspiration. Deadlines are more useful. Ideas come if they have to. Give yourself deadlines.
What type of songs do you want to write? [Let's leave "compose" out of it for the time being.] How many types of song do you know? Do you want your songs to be unusual ones or the usual ones? Will the lyrics be an important or an unimportant part of the song?
At the moment I'm working on (I should be working on) these lines: He runs a racket here, capiche?|Some Ponzi scheme to fleece the nouveau riche". The 4-beat/5-beat structure is a useful restriction on the music. And the meanings and the sounds of the words suggest certain types of chord and tune.
Restrictions are always useful. Try making up two or three new chords and restrict yourself to those. Or try finding two chords that don't go together, then find intermediate ones that link them.
Hurry! Try and do one or two very short songs a day. Open novels at random and find a line to get you started. I just did this. Third try I got "I heard them talking, clear as anything, heard every word." [P.55 Kazuo Ishiguro's Never Let Me Go"] The first line of a paragraph seems to work best.
What you can't do is follow a chord progression that someone suggests! There are millions of songs out there already, and millions of chord progressions to match them. Until you listen to 'Axis of Awesome'...
Just about any chord could follow any other chord to become a sequence, so that's not a bad place to start. A lot of songs have started thus, and become very popular. At a simpler end of the spectrum, many, many songs only use two or three chords - thousands of 12 bar blues songs are testament to that.
Use your moods to influence your writing. If something makes you angry, fed up, ecstatic, frustrated, use those feelings to spawn songs - words particularly.
Noodle constantly. Record noodles. Come up with phrases, which may or may not fit together, but could be part of a chorus, verse, etc.
Play with others. A lot of songwriters work better collaborating. So work with others. Both better and not as good as yourself.
Learn how to actually put down musical ideas on paper - yes, proper music writing. It's another aspect, and can help formulate ideas, and it certainly makes it easy for others to read and play what you've produced.
There is no rule on music composition. All rules are made to be broken.
Songwriting is a Decision Making process. You create, you listen, you like it/deslike it then keep it or change it.
There are many songwriting thecniques and approaches. The more you try, the more you learn what works for you. I advise reading 101 Songwriting Wrongs And How To Right Them, by Pat Luboff and Pete Luboff.