Some tips on keeping a coherent theme in your game audio

As an Audio Engineer, and a Composer, the concept of continuity in overall design is very Important.  Music that fits and sound effects that fit the genre and tempo of the game are essential for making a solid gamer experience.
 
For example pixelated 2d art and eye popping effects, or vector graphics have an expected sound styling that goes with it.  If you have epic Modern Warfare style soundtrack placed with the game it would be a tad bit awkward even if the production was solid and as sharp as a tack.

Composing a themesong and reusing it in different ways in subtle usage in different musical scores can help tie themes together, for example the music in Super Mario world you can hear one simple and repeating theme in all the music.

Keep a close eye on the artist's angles and let the concept art, and game concept inspire you.  This includes your folley.  You should havea spreadsheet of all the available events in your game with your personal notes for each event on how to achieve the sound effect you need, whether you need a bunch of potatoes and m-80s or a latex glove with a bunch of grapes.  Maybe even a Korg MS-20 or some odd and unique synthesizer that will make the chunkiest retro effect you can muster.

Usually the audio comes in during the late stages of development, so what you can be doing in that time is composing the score!  be sure you know what the High concept ofthe game is, if the art takes you in a new direction then you may have to do a change in instrumentation, and maybe some arrangement changes.  Hang in there, Audio can be stressful if you don't have a clear idea of what your client needs from you, and you will get lots of feedback, you may or may not like.  It's time to swallow your pride and just go with what they say they like most!  Or maybe they are short on time and they will have you drop everything and move forward.

So here's how I deal with that.  I like to do several instrumentations so that there is a selection they can chose from out of group, then they can request any small changes to the one they like.  THat way it opens options if they change thier minds later.   Keep on top of the game design so that you know if there have been any updates to events that require sounds, and put your best effort forward.