Remember last year, when you had to drive all the way to town to get a special cotter key for the planter, that cotter key that couples the planter's transmission to the drill shaft that drives the seed units?
(Okay, you didn't drive to town. You used an 8-penny nail you found in the bottom of the tractor's toolbox, but you get my drift.)
Different planters have different "wear items," but there are few universal parts and tools that are useful to take to the field when planting. For example:
-A cotter key assortment. If you plan in advance, add to that assortment multiples of the most common cotter keys used to connect assorted driveshafts and transmission shafts on the planter.
-An assortment of hardened roll pins. Same strategy.
-A roll of mechanic's wire (aka, baling wire). To run through/around roll pins or cotter keys when they don't fit tight in their egged-out holes and keep falling out.
-A hammer and a couple punches. Long, thin punches are nice to drive out the remnants of the aforementioned pins/cotter keys when they shear off inside driveshafts.
-A couple Crescent-style adjustable wrenches, to turn hex driveshafts for alignment or other reasons.
-A seed tube brush or some device to clean seed tubes and seed tube sensors.
-Contact cleaner or other spray cleaner to flush dirt, grease, dirt and grease, or generic gunk from electrical connectors to improve electrical flow.
-WD-40, JB-80 or other spray lubricant to aid repairs requiring sliding a driveshaft in or out of a bearing, seed drive transmission or coupler.
-A small tube or tub of waterless hand cleaner, preferably without pumice or grit. If you have an air planter and have to replace/install a new hose over a barbed fitting, waterless soap is a great lubricant. WD-80, JB-80 and other petroleum-based lubricants may attack the plastic or rubber of hoses, so avoid them when lubing hoses and hose barbs. And the hand soap is always nice to have handy after changing a wheel bearing.
-the planter's owner's manual. If nothing else, have the local office supply store copy the pages pertinent to transmission gear settings, speeds, and air pressure/vacuum settings. Then have th office supply store laminate those pages so they're water and greasy-finger resistant.
Think back to last spring and recall the pieces and parts you either had to run back to the shop to get, or send the wife, kid or hired man to town for. Those are the pieces and parts to have in your toolbox when it's time to start planting.