developing a fugue

In general, every statement of the subject in the fugue should be answered by the same theme shifted up or down in pitch, usually, (but not always) to the dominant (and sometimes tonally modified to keep it in key) until every voice has stated both the subject and answer (with or without countersubjects). After that, the opening section (exposition) can be completed and the much freer development section can begin without the strict tonic-dominant, subject-answer formula.
Subjects can be modified and answers can be reversed, inverted, transposed, etc.

A lot of variety is possible to the extent that some authorities don't include 'fugue' as a musical form but as a contrapuntal texture.

I completely agree that it should be considered more of a tool than a song type. I was just sitting in class wondering how to end this piece ive been working on and then it hit me, it could be a fugue. And I ran home and tried it and it worked really well. It just instantly creates these new and intresting environments to develope. Im really excited to see if I can pull this off thanks for the help.

I've only tried to write one so far, but I found it much more striking when I did not modify it to stay in key. Does it just clash for certain melodies or something?

Answers can be 'real' or 'tonal'. 'Real' answers are exact transpositions of the subject and will often force a change of key. Tonal answers avoid that by modifying certain notes to ensure that it stays in key.
Say you're in the key of C major and the subject opens with C - B - A - B - C. It can be followed (in another voice or part) by a real answer G F# E F# G OR a tonal answer G F E F G.
The 'real' answer with its 'out of key' note, F# is now more likely to clash with whatever the original voice is now doing - but it's up to you to decide to include the clash and make it 'striking' (as you found yourself) or avoid it by either:
1. Using a tonal answer as it has no out of key notes - (less striking but melodically more varied as the answers are never exact transposed repetitions of the subject.)
2. Using a real answer but choose new material for the original part that won't clash too much with the real answer - (That gives you more control over the severity of the clash).

The essence of a fugue is contained in the name, which means 'flight', not derived from the verb 'fly' but from 'flee'. Think of those wildlife documentaries where you see a leopard chasing a young gazelle. The gazelle runs for its life, twisting and turning, and the leopard follows every move (real answer). But sometimes it moves differently (tonal answer) which results in either an advantage or disadvantage for the leopard, depending on its skill at calculating such changes . Aside from hoping the poor gazelle gets away, most viewers (listeners) are fascinated by the intricacy of the chase with its constantly changing directions through an ever changing landscape - and I think this analogy has now reached its absolute limit. :lol:
The point is, use your skill to keep the chase fascinating - predictable enough to let intended listeners guess where you're going, but unpredictable enough to surprise and delight them just as they think the chase is over.

Thats a great analogy, I hope I can do it justice haha.

"2. Using a real answer but choose new material for the original part that won't clash too much with the real answer - (That gives you more control over the severity of the clash)."

I think i'm going to write it that way after letting the subject and answer full crossover once. The song i'm writing is called "little red riding hood" and the idea was to tell the story of little red riding hood in 5 minutes and 0 words. The part that I wrote for the hunter when he comes is where im going to put the fugue to try to convey the battle between him and the wolf.