Person, thing, matter, place
The four general nouns that let you talk around any word you don't know.
hito
person; people; others
人 ひと
Any person or people, usually with a description in front (ii hito, ano hito), and hito ni yoru means 'it depends on the person'.
suki na hito, iru?
Is there someone you like?
好きな人、いる？
suki na hito, imasu ka?
Is there someone you like?
好きな人、いますか？
People take iru, not aru: hito ga iru.
mono
thing, stuff
もの
A concrete thing, usually with a description in front, so you can name what you lack the word for (taberu mono, hoshii mono).
suki na mono tanonde ii yo.
Order whatever you like.
好きなもの頼んでいいよ。
suki na mono tanonde ii desu yo.
Order whatever you like.
好きなもの頼んでいいですよ。
mono da at the end means 'that's just how it is' (sou iu mono da).
koto
thing, matter; about X
こと
An abstract thing such as an act, event or topic (suki na koto, sonna koto), X no koto means 'about X', and it is the base of patterns like -ta koto ga aru.
suki na koto shite ii yo.
Do whatever you like.
好きなことしていいよ。
suki na koto shite ii desu yo.
Do whatever you like.
好きなことしていいですよ。
tanaka-san no koto ga suki means 'I like Tanaka-san'; X no koto turns a person into a topic (about X, X as a person).
tokoro
place, spot; side, trait
ところ
A place (ii tokoro) or a trait of someone or something (yasashii tokoro = their kind side); X no tokoro, casually X no toko, means X's place (tanaka-san no toko ni iku = go to Tanaka-san's).
suki na tokoro de ii yo.
Wherever you like is fine.
好きなところでいいよ。
suki na tokoro de ii desu yo.
Wherever you like is fine.
好きなところでいいですよ。
You can't go ni a person: tomodachi no tokoro ni iku, not tomodachi ni iku. The aspect pattern -tokoro (tabeteru tokoro) is a separate card in A.