"Want" is direct and simple. Use this when you are definite and stating a fact. However, be aware that being direct may also sound rude and selfish.
"Would like" is suitable for requests and wishes. It is indirect and polite because it expresses something imagined (subjunctive), not something factual and direct.
For "I think", you could also use "perhaps", "it seems that", "in my opinion", "as I see it" and many other expressions. For "I feel", it sounds more emotionally-based if you don't want to use a cold and logical "I think".
It's best to know how to use several expressions, as they do have subtle differences. Don't rely on just one phrase.