Distinguish そうです for appearances and reported information.
The rule
The appearance form is particularly attached to the ます base of the verb or to the radical of the adjectives in い: おいしそうです (it looks delicious). The そうです of hearsay is placed after a neutral form: おいしいそうです (it seems that it is delicious).
Examples
このケーキはおいしそうです。
This cake looks delicious.
このケーキはおいしいそうです。
I hear this cake is delicious.
雨が降るそうです。
I heard it's going to rain.
Remember
- ます Radical without ます + そうです: appearance ("appears").
- Neutral form + そうです: reported information ("it seems like").
- The difference can be seen in 降りそうです / 降るそうです.
In everyday life
雨が降りそうです。
Looks like it's going to rain.
明日は雨が降るそうです。
I hear it'll rain tomorrow.
Common mistake
おいしいそうです is incorrect for "it looks good": say おいしそうです.