You need to be much more specific about what these "general characteristics" are.
In NLP "general characteristics" of a sentence can mean a million different things - sentiment analysis (ie, the attitude of the speaker), basic part of speech tagging, use of personal pronoun, does the sentence contain active or passive verbs, what's the tense and voice of the verbs...
I don't mind if you're vague about describing it, but if we don't know what you're asking it's highly unlikely we can be specific in helping you.
My general suggestion, especially for NLP, is you should get the tool best designed for the job instead of limiting yourself to a specific language. Limiting yourself to a specific language is fine for some tasks where the general tools are implemented everywhere, but NLP is not one of those.
The other issue in working with Twitter is a great deal of the sentences there will be half baked or compressed in strange and wonderful ways - which most NLP tools aren't trained for. To help there, the NUS SMS Corpus consists of "about 10,000 SMS messages collected by students". Due to the similar restrictions and usage, analysing that may be helpful in your explorations with Twitter.
If you're more specific I'll try and list some tools that will help.
