I found that when I played this game solo using normal rules it was far to easy. I tried a few house rules mixed in with some vaiants by other people and had a much better game.
This is what I've tried:
1. Use the 'Alanta be Damned' Variant, I like this one.
2. Don't start with any followers
3. You can only use a maximum of 5 resources per turn (e.g. if you use 2 food to heal, followed by 2 gas to move, you can then only use 1 ammo during an encounter etc).
4. If you roll a 'blam' result you place zombie token at every adjacent hex. If you roll 'Blam 2' you place token at every hex within 2 hexes of you. If you roll 'Blam 3' place token on every hex with 3 hexes of you.
5. One of the resource cards says that you can destroy all zombies within 3 hexes of you, I reduce this to within 1 hex.
6. When using the 'Atlanta be Damned' Variant, to complete the first 2 locations (gun shop and stadium) play them as if they are your 3rd location (follow directions printed on bottom of locations).
7. For the third location, choose the location only after you have collected the 3 follows that were placed at the start of the game AND after you have collected the first 2 locations. Make the 3rd location the the most difficult location to get to (generally the one with most zombie tokens between location and yourself), then follow rules on Atlanta be damned scenario (the part that says '...to make game harder try this for 3rd location...).
I've only played using the above once and it took a bit longer and was more difficult. I enjoyed it much more than standard rules!!