You need an area with already high base appeal. The more tiles have 4 or more (Breathtaking) the better. Then you have to carefully plan your preserves for this era. Each city can build one so if you can cluster 3 or 4 cities around the areas with high appeal its best. You aim for one tile inbetween perserves so a triangle shape is best with a free tile in the middle and preserves at the edges because the yields stack if a tile is adjacent to more than one preserve.
Keep in mind that the preserve itself does NOT give any yields to the adjacent tiles, you also need the buildings (which apply yields to all surrounding tiles). The first one comes pretty early and gets you food, faith and culture. The second one is way later in the civic tree and provides gold, production and science.
To increase your appeal up to 4 (you get the full yields once a tile has 4+, if a tile has 2+ those are greatly reduced and you wont get any beneftis if you have less than 2 appeal) you can
- build districts providing appeal (HS, TS, EC, Water Park, Dam, Canal) next to them (perservers itself increase the appeal of surrounding tiles by one as well, but since you plan around those they should be in there already)
- plant woods (woods will also add production to the tile) on these tiles or adjacent
- chop rainforrests and marshes on these tiles or adjacent
- avoid districts reducing appeal (IZ, Encampment, Aerodrome, Spaceport) next to them
- build improvements providing appeal on or next to them if you have access to any (e.g. the Persian or Egyptian UI)
- build wonders next to the tiles
- build the Eifel Tower
- get the two great engineers that provide appeal (those are pretty late into the game though)
- bull moose teddy can raise his appeal if he builds a national park in the city
National Parks work quite well with preserves in generall since both need high appeal tiles without improvements.
The Incas can use mountains well for this strategy since mountains always have 4 appeal.
Even if Earth Goddess was nerved it is still good if you build alot of preserves/high appeal tiles and makes the tiles even better.