There are some BPLers who spend more time at GCNP and go further afield, but from my dozen trips, mostly along the main trail corridor (in no particular order):
Any time spent at altitude immediately prior to your trip helps you acclimatize. Â Rather then drive up from Phoenix/Vegas and start hiking, I’ll arrive the night before and stay in Tusayan 5 miles to south. Â Red Feather Lodge is an affordable but modern option there.
Trim your toe nails 3-5 days in advance.
Use shoes with a serious amount of toe room. Â But minimal heel slip. Â Half the time, you’re heading downhill. Â The other half, you’re climbing.
March often still has snow on the upper portions of the South Kaibab and Bright Angel trails. Â Early April would still have some on the North Kaibab. Â Microspikes are as much as I would suggest, but my daughter (11 at the time) and I just used trail runners the last time we were there (Grandview Trail in March. Â Yes, she’s wearing shorts. Â We’re from Alaska):

South Kaibab in March, one mile in, snow is starting to thin out, we didn’t use any spikes, although Clorox rubbed on your soles will soften/sticky them up:

BA tends to have more snow in Spring than the SK which gets more sun so check it out the night before. Â The BA is definitely easier to hike up (less steep, more (i.e. any) water stops) and the while there is a shuttle bus between the two, it doesn’t run early nor very late and it’s a pretty long hike between them when you *thought* you’d already finished your trip, IME!
I’ve never had a problem finding parking around the Bright Angel lodge within 1/4 mile of the BA trailhead. Â At least not at 4 am when I’m usually starting my hike.
There are no bears but lots of other critters who’ll try to get into your food. Â Either sleep with it all or, if you cache any, use a cookie tin (like those “Danish Cookie Assortments” or the Christmas gift tin of “gourmet” popcorn your sales rep gave you). Â Available, empty, at thrift stores for $1:


I find applying creek water to a bandana or high-absorbancy neck / forehead sponge is less tiring than sweating out the same moisture. Â To the point of bringing a pint “dirty water” bottle that I don’t treat, but use to cool myself on during the uphills.
Check which water sources are on as you descend the BA. Â If they’re all on, you only need enough water to get from the River to Indian Gardens (which could be a pint early in the morning if you camel up or 2-3 quarts if it is mid-day in a heat wave – I’ve had 90F in May). Â Above Indian Gardens, 3-mile and 1-1/2-mile shelters will (or will not) have water.
Do you have your permits? Â Or a plan to queue up for walk-up permits? Â Permits are hard to get for the trail corridor. Â One option a UL backpacker might have is to LOOK like a day hiker and stealth camp. Â It’s hard to find a place to hide, but once it gets towards evening, you wouldn’t need to be far off the trail.
Do hills around town to get in condition. Â Lots of hills. Â Not a stair-climber at the gym – those only go up, and the GC is half going downhill. Â If there aren’t hilly trails nearby, then go up and down real stairs in your house or at office building / apartment / hotel in town. Â The more I do that prior to a GCNP trip, the better it goes.
Bring a few pinches of alum if you need to settle sediment out of water prior to UV or chem treatment. Â You’re unlikely to need it, but a rainstorm can cause all the creeks to run muddy for a while. Â Here’s a write up on it:Â https://backpackinglight.com/forums/topic/72551/
I’d go no-cook on a trip like that.
The grocery store on the South Rim is surprisingly well stocked. Â 30 brands of micro-brew beer, deli sandwiches, minor first-aid supplies, isobutane canisters, micro spikes, 4-point crampons, a reasonable selection of real, name-brand backpacking stuff at REI-ish prices (not super cheap, but not gouging you). Â Call ahead if you are counting on a particular stove fuel – I’ve seen them run out. Â Or get it at an REI or Walmart in Flagstaff or Vegas after you fly in.
When flying into Phoenix or Vegas, I go to Trader Joe’s and get a soft-sided cooler, a bunch of pre-made salads, wraps, and their dried-fruit/nut gorp mixtures. Â I eat the salads while on the road and use a wrap or two as my first day’s trail food.
While I like a Chrome Dome umbrella in the High Sierra in the summer, in the Canyon, I usually use a wide-brimmed hat. Â With a chin strap, because winds can come up. Â Less important in Spring than in Summer, but coming out of winter, if you don’t have any base tan, be careful.