Use Spliit App (open-source, web-app, mobile app) for an easy way to track and split expenses with a group.
This might seem like the most mundane tip, but it's incredibly useful: In 2010, I went on a football trip to England with some friends, and we wanted to keep track of expenses—like who paid for the beer at the pub. At that time, we used an app called "Share-a-bill". It worked really well; inputting information on the phone took only seconds, and in the end, I sent out an automatically generated email with an overview and resolution of the costs (see these screenshots).
Since then, I've used Share-a-bill multiple times, but the app hasn't been updated in years, making it difficult to collaborate and share individual expenses. It turns out that expense tracking has become a full industry with mostly commercial options such as Splitwise and Expensify. However, "expense-tracking-as-a-service" can be costly and frustrating for everyone involved. When an app's primary incentive is profit, the straightforward process isn't necessarily optimized for the user.
Recently, I found Spliit App, an open-source app (both web and mobile) that doesn't require any accounts: you can set up a group with some details like name, participants, etc., and it will create a unique and secret URL, which you can share with the group.
The developer is pretty open about Spliit's growth, expenses, and funding and wrote a post about its usage statistics, costs, and community donations.