You’ll usually know in advance how you’ll receive your race pack so check the website of your chosen marathon. Some still send the packs by post but most require you to collect it either in advance or on the day. What facilities will be available at the start line? How long will you be st the start line for? Most big races allow you to drop a bag off at the start line and it’ll be taken to the finish line for you to collect.
During the race
Supporters! Depending on which race you’re taking part in, there may or may not be supporters on the route. There’ll likely be parts with very few supporters so think about how you’ll stay motivated during those parts (music might help, if you’re allowed headphones).
Arrange somewhere to meet your loved ones in case you can’t use your phone. Ensure you have something available for a refuel as you’ll probably be hungry before long. You’re usually given water or another source of hydration at the finish line but it’s worth putting something in your bag, if not.