I often have trouble writing good melodies, ive had a few ideas for a melody but just a melody :(. I would love to mae my melodies into a concert band peice but it never seems to work. so I need some advice on melodies and how to write them using harmony and etc.

I find it easier to write a melodic line without any harmony first, this give you more freedom melodically. When the harmony comes first I think the melody it may sound less interesting due to restrictions you might be doing with the harmony and trying the melody to fit in. But everybody works different and everybody gets the things in different ways. I tend to do it in both ways, sometimes I start with harmony and others with melody. Then to find the chord that will fit better to the desire or purpose I have for the melody.

Don't forget your melody don't need to fall on the strong beat always and don't need to play the notes of the chords always. And to include a cadence in the end of it. Also look for a rhythm that can follow through all the melody or look for a small motif that can be repeated various times and in variations. Or try to use your visual campus to visualize images of what you want to represent in music and to try to look what kind of sound would fall perfect for that visual. And try to avoid those tiring long notes sustained! ;)

Keep making melodies, you will see with time maybe you will find a pattern in yourself and will be easier for you to make a melody that can sound pleasant to you.

Yes. Just like most-to-all things, it just takes practice. Over the last couple of years I've gotten better at improvising things, that it's so much more of an effort to write down my things, but anyway.. What Nyu said before was pretty much correct. The norm. is to write a harmony/chord progression. The other is to add a harmony to an already-written melody. I, myself, cannot create a melody without a progression (specifically) and I cannot create a GOOD melody without an OUTSTANDING progression... yet... I cannot even create a progression with a melody or vice versa, I need to make them at the same time, because that's just how I work.

You see, you can make a melody off a progression or harmony, and you can make a progression off of a melody; you could just be like me and have it all hit you at the same time or have enough "practice" to pull anything you'd like out of your arse.

Good luck with that melodisism training.