Particle は/が: as for…

は (spoken “wa” not “ha”) = “as for”, “is”… Jo は student desu = as for Jo, he is a student
neko は kawaii desu = as for the cat, it is cute = The cat is cute.

は is placed after the subject.
Subject + は = as for [subject] / [subject] is…

Make it a question:
neko は ikura desu ka? = as for the cat, how much is it? = How much is the cat?

が is basically the same, but stresses the subject (the part BEFORE が). は stresses the part AFTER the は

は talks about something.
watashi は Jo desu = I am Jo

が identifies something.
watashi が Jo desu! = I am Jo

Use も instead of は to say “also” / “too”.

この ねこ は かわいい です。その いぬ も かわいい です。

this cat is cute. that dog is cute, too. 

Desu and the likes: Present/past positive and negative

です (des(u)) – it is, present positive
でした (desh(i)ta) – it was, past positive
じゃありません (jaarimasen) – it is not, present negative
じゃありませんでした (jaarimasendesh(i)ta) – it was not, past negative

Sentence order: 
です comes at the end of a sentence.

Noun + です = Noun, it is
山です = Yama desu = Mountan, it is = It is a mountain

Make it a question