The decoration of language in proposal writing I am a newbie to proposal writing although have been writing research papers for several years. After the rejection of my first NSF proposal, I am becoming aware that the proposal language is quite different from research paper language, where the later one emphasizes on its accuracy and objective, while the former one, according to my current understanding, needs more fine-tuning on the "tone and the sales pitch".

I guess that's where the decoration of language could  come into play. Could anyone shed some lights certain systematic approach such that I can train myself and master the needed skills? Or, is there any systematic approach that can quickly turn my research paper-style proposal by setting the mood and tone as a "sales pitch."

I am not a native speaker and that could be hard, I guess. Any suggestions would be appreciated very much.
While not quite the systematic solution you are looking for (which I don't think exists) here are some ideas. This is a matter of knowing your audience and a matter of practice. I suggest that you do a combination of all of them:


Review Grant Proposals. I warn I speak from the UK system so things are certainly a bit different elsewhere, but there exist a number of opportunities to serve as an expert reviewer for grant proposals. You may be at an early career level, but some granting bodies specifically seek out early career reviewers (e.g. the AHRC peer review college in the UK is one example). Contact granting bodies directly and ask to be added to their database of reviewers and when you are asked to review grants, pay very close attention, first, to the standards against which you are meant to review, and, indeed, what works on you...what type of writing in the proposals wins you over. Attend any training days etc that the granting body offers for reviewers. I do note that you are in the USA, but I've peer reviewed Fulbright and other USA-based proposals, so the opportunities are there.
Read successful grant proposals. Read a lot of them. Note the style and tone of the language. If you have a colleague or friend who has had a successful NSF, ask to see their proposal. Contact your University's research office and ask for copies of any successful large grants. You may think that this is crossing a boundary or that people don't want to share their grant proposals, but it is totally normal. I was successful at applying for a very large (€1.5mil) grant last year and over the course of the year I must have shared my proposals with 30 other scholars who wish to apply to the same scheme. I have done the same with previous successful grant proposals. 
Familiarise yourself with the differences between granting bodies as this will govern the language style and tone you should use. Funding bodies that want to fund blue skies, high risk-high reward research tend to like language that fits the edgy nature of the grant. Funding bodies that prefer you to, essentially, know the outcome before you start like assurances and less "excited" language. When in doubt, you can talk to the grant manager about the motivation behind the grant and then think about how that might translate into your language.
Lean on whatever resources are at your University. That might be the research support office or equivalent. It might even mean an external consultant that the university hires to help develop and prepare grants. Make sure you know what is on offer and take whatever is available.


Good luck!