To begin with, Dhoni should abandon the sheet anchor role he has adopted of late. He left Chennai high and dry after taking 29 balls for 28 runs in the IPL semi-final and then getting out. He did the same against the West Indies. There’s no point keeping so many wickets in hand for the last four overs, because one low-scoring over out of those will upset such calculations. It's after all, a 20-over game, and I don't remember the Indian team pulling its shutters down every time a few early wickets fell in the first World Cup.
Second - play the in-form RP Singh, highest wicket-taker in the just-concluded IPL, in place of Ishant Sharma, who seems caught betwixt attack and defence in T20 cricket, and has been a flop for Kolkata too. Ishant needs to go flat out with the new ball keeping two slips in place. But, for now, since that's not something they've worked out yet, it's best for him to be a spectator.
Third - play Dinesh Karthick, a prolific scorer of late for Delhi, instead of Irfan Pathan, who is cannon fodder at his pace, and has been no great shakes with the bat either recently. The full complement of seven batsman will allow natural strokemakers like Dhoni to play without fear of a batting collapse. After all it's Virender Sehwag who's missing, one of our best hitters. Why should a bowler take his place?
Dhoni said at the start of the tournament that part-time bowlers like Yusuf Pathan, Yuvraj Singh, Suresh Raina and Rohit Sharma (all of whom were great successes in the IPL) would play a key role. So then, drop the extra bowler and use them. Yuvraj, Raina and Rohit have hardly got an over yet because we're playing so many bowlers. For some inexplicable reason India keeps disturbing its team composition of six batsmen, wicket-keeper and four bowlers to play the extra bowler and it almost never works.
Finally, it would be best for Dhoni to take bowling if he wins the toss, because in the current pusillanimous frame of mind he is in, India is more likely to underachieve while batting first, or over-correct and commit harakiri.