I had really gotten inspired with fairy doors as portals, so I made a few from sticks, stone, bark and leaves to scatter around my yard, away from the path of the lawn mower. Wind and weather have flattened them over the years. One still stands, so I think they like that one. It has pieces of rose quartz with it, and has been under my lilac bush for years and years.
I think I'd do a shimmy-dance if I stumbled across a fairy door out in a park or trail.
I had a calendar with a dif pic each month of fairy houses & doors. You can make fairy sugar as an offering: use a base of powdered sugar, then add lots of flower petals and some candy sprinkles from the grocery baking isle. You leave a spoonful here and there, using leaves as platters. This tip came from the fairy house calendar.
I made a fairy-kit for my neighbor's 9-yr old daughter. it had all the supplies, glitter and bling for making clothespin fairy dolls, and one finished one to show her how. Everything was pre-cut for her. And a glue stick was included. There was a pocket sized fairy diary to write about her meetings with fairies and glittery pen, instructions on how to look for fairies and recipes for fairy sugar, fairy tea and cakes (aimed at her mom, of course). I had shown it all to her mom first, and made sure glitter was allowed. Also included instructions & a green plastic container for making a wish bottle. It was all stored inside a cigar-box kind of pretty box. To anyone without imagination, it was a box of cloth scraps, clothespins, and an empty Excedrin pill bottle. Just add fairies, and see how different it became.