http://classicalmusicpiano.files.wordpress.com/2012/01/leaving-certificate-music-composing-pdf.pdf
I composed this a few days ago. It's practice for my music exam in school and we have to compose a 16 bar melody. They give a 4 bar 'intro' as a guide.
Please tell me what you think of it.

As a very first composition I'll say it's a worthy effort. No one writes a masterpiece on the first try. I do wonder if you were limited to two parts by the assignment?

Your first bar starts out pleasant enough, but the jump from the a down to e to start bar 2 is weak and puts you too close to your bass line for comfort. But I really wondered at that point why not echo your first bar with c# a e a f# g# f# (or e)? Beyond that I'll simply suggest that you strive for continuity and smooth transitions (and maybe fewer harmonic changes). Also, reuse strong melodic ideas more (your first bar is actually pretty good).

Finally, the key of e major is as good as any other, but is not usually used for simple pieces such as this. I'm curious what motivated this choice.

One last point, in your last bar the bass would be stronger of it went down to the e below the bass clef (IMO).

I have to agree, this is really a good effort as your first composition and through complex practices and a wider view, you are surely on your way to coming up with even greater ones.

I sure hope that further motivation will move your forward, though you have to remember to couple that with the right choices so that you can make your pieces sound more intricate.