Hi there
I recently completed my first marathon, and being a novice runner was dreading hitting the wall.....well, to my shock, it never happened! I ran a negative split, and my last 3 miles were infact the fastest. Here's what I did...for what it's worth.
I consumed loads of fluids in the week leading up to the race, and carbo loaded only on the last 2 days. I am assuming you are on top of this already so onto the race itself. I ate breakfast about an hour before the race started, and throughout the race I had 1.5 litre of energy drink, plus water. I had a gel at every hour (for me that totalled 4)...every half hour I had a couple of haribo sweets (or 2 lucozade enery sweets), and just basically kept this up all the way though.
I always find that I have more energy if I eat quite soon before the start (not immediately though!)...but close to it, I think I have more energy to burn (cos I must burn loads of it off with the worry too LOL!).
FYI I used a combination of gels....2 SIS orange ones, and 2 Powerbar blackcurrant ones (which contan caffeine). These really seemed to do the trick for me, as did taking on lots of fluids. I am convinced this helped me not hit the dreaded wall. In the end the marathon was nowhere near as bad as I had thought it would be....I was dreading it!
Good luck