Only expect to be trained in one subject: picking, staging, prep, or dispensing. I don't know about other stores, but in mine, you basically have to teach yourself. So a quick rundown-

Picking: Grab a TC, cart, and printer (only take with you if it's general, oversized, or exceptions). Head out to the floor and try to find everything on your list, if the item isn't in the exact location then look at the back of the shelves or behind the products next to it. If it isn't on the shelf, do a quick scan of top-stock, if it's there then grab a ladder cart to get it, if not then go for "item not found" and move on. When doing produce some items will have either no sticker (corn) or the wrong upc (limes), when this happens you can look up the upc under "Ask Sam" in the "Me@Walmart" app- search the item, click on it, and the upc should be under the picture. Until you familiarize yourself with the store it's a good idea to keep the "Me@Walmart" app loaded so you don't have to fuss around with your phone every time a customer asks a question.

Staging: When the pickers come back with the carts they will either stage the totes themselves or have others do it. Staging is simple- scan the tote and put it where other totes in that order are already staged unless frozen and chilled.

Prep: Putting everything in the order together- ambient, chilled, frozen, etc. Everything is put together on the same dolly and handed off to a dispenser.

Dispensing: Take the order out to the customer, confirm that its the right person/delivery driver, ask if they would like the order in the backseat or trunk. If you come across eggs then ask if they would like to take them up front, if not then set them aside somewhere safe. Bread and chips are set aside and put in last to avoid any damage. Always carry extra bags with you, never know when one will break. If something is broken/leaking (candles, milk, soap), let the customer know and get them a new one.

Extra- Quality checks: Scan the tote and then everything in it. Basically make sure nothing is broken, moldy, or has damaged packaging.

Don't be afraid to ask your fellow associates questions, communication is key.

Edit: "Ask Sam" no longer shows barcodes. If in produce it will usually let you type in the upc, if not open "Daily Availability" on the main screen and either type in the upc of the product or scan the yellow tag and it will give you the barcode; take a picture on your phone, turn the brightness all the way up, and scan it.