It happens to me all the time- I think I'm going to get an hour to setup and sound check, and a few seconds after I've hauled my gear into the venue, a frazzled mix engineer rushes onstage and asks if I can sound check in two minutes.
I've been a huge proponent of a lean, bullet proof keyboard rig since I first started gigging, and here are my 10 best methods of reaching that goal:
1. Create a list at home of all your gear.
As you pack, check each item off of your list. This will keep you from leaving cables at home, and help you to pack more efficiently.
2. Bring a sub mixer.
Use it to combine all of your keyboard sends into a single output, so you don't have to run multiple outs to the FOH mixer.
3. Buy gear that's reliable and streamlined.
This seems like a no brainer, but it's essential to buy equipment that works every time, and is simple to set up. I literally count the cables I'll have to use for every keyboard I buy- if the count is too high, that's a big consideration in my purchase.
4. Pack two bags, one for replacement cables, and one for your main cables.
Leave the extra cables in the car, just in case. This will save you from making a time-consuming run to the local music shop before a set.
5. Bring your own amp.
If you wire it right, you can use this to monitor yourself and the rest of the band. In small venues, this might be the only amplification you need onstage, giving you more control over your sound and simplifying the engineer's job.
6. Bring your own direct box.
Don't rely on venues for DI boxes. Bringing your own makes your setup go more smoothly, and will keep the mix engineer from having to burn time hunting for DI boxes in the back.
7. If you're running stereo, get combined stereo cables.
A combined cable is faster to plug in, and faster to pack.
8. Get good cases.
If I'm in a rush I usually get a bit less careful with my gear, occasionally banging stuff and nicking edges as I get things into place quickly. Having quality cases helps ensure you don't ruin your gear before you even unpack it.
9. Give yourself time.
Always, always budget more time than you think you need to get to the venue. Last week I had a gig in another state, and I allowed an extra hour to get there than I thought I needed. A massive traffic jam and an emergency stop at a Walmart later, I walked in with 15 minutes to spare.
Rushing only makes you sloppy, and will often lead to more work in the end.