Once ive become to add comments on Google Maps for places i visited and even didnt think then that that was a moment when i became a local guide. It is not so hard to make some notes about any place or object you see right now or even share some photos. In this way you help others to know more about place or something they didn`t know earlier.
Somehow i faced an app Google Trips. If you still dont know about it i would strongly recommend you to get it - i believe it is one of the best applications for travellers. With it help i can see top spots in a place where i plan to go to, make a list of spots i want to visit, all booking information (reservations, tickets, hotels, etc.) and more. Another words it makes your trip rather more easier to plan. As it based on Google Maps you can see your day plans right on the map, moreover it shows your saved places to visit so you will never lose your way and wont miss each spot you planned to see and make photo with.
I underlined for myself the importance to make notes on Google Maps after my trip to Lisbon last year. On one of the days i with my friends came to have a dinner in a cozy place in the city center. But unfortunately after visiting that place each of four of us had a stomach problems and spoiled next day of our vacation. When later i found this cafe on a map and found that we were not the only who faced the low-quality food there. Nevertheless i love Lisbon and it is one of my favorite cities.
So i make notes, comments, share my impressions and even photos on Google Maps first of all to help people to make their choice as accurately as possible being in some place first time.