There are many apps and websites that players can use to look up rules during game play. But, beware: once those phones come out, it can be a slippery slope of temptation to tune out.
Go fast without the distractions by using Page Flags. Players and DMs have an age old tradition of flagging the pages of their sourcebooks to make it easier to reference key material. Page Flags honor that tradition by doing it one better. Rather than hand-written labels, Page Flags are neatly printed words and icons that are specifically made for individual 5e books.
Page Flags combine a common Japanese method of folded-over tape with the ubiquity of sticky notes. The result is fully-customizable flags that are worth showing off, feel great, and hold up to usage.
On game night, a "rules lawyer" with the right sections flagged can turn out to be actually helpful. But, even before game night, flagging pages gives players a sense of mastery over the material and calms our human need for organization.
How to Make
Paper crafting difficulty: Easy.
Pay what you want for the templates at DMsGuild.com. You will also gain access to Google Spreadsheets that you can copy and edit.
Select sticky notes that you already have, or order some in new colors. Or, use washi tape.
Use the included words and icons, or customize with your own. Print at home. Make as many as you like.
Follow instructions to cut out, fold, and stick on.
Game Night Advantages
Gain advantage on attempts to flip to the right page.
Know that you are ready for any situation... that involves looking up rules.
Keep players hands and minds in the game with a quick reference tool that comes without temptation.
Add personalized value to your books to make them truly your own.
Gift them to your DM or players as a sublte sign that you are more hardcore than they will ever be.
Neat tabs on pages
Make my fingertips tingle