(Disclaimer: This is purely from a layman point of view..more experienced political minds can feel free to point out any deficiencies or better yet add on their ideas):
In no particular order:
1. Differentiation: He should totally differentiate himself from the current system. He should go out of his way to portray himself as coming from outside the system. He should be aiming to form his own political party and not join any of the existing ones. He should market his party as the youth vehicle.
2. Build a Good, Diverse Team: He should build a team of intelligent, ambitious, passionate people, preferably young (but not necessarily so). Countrywide. If possible as many of these people should also be fresh faces. He should recruit people who will really believe in him and his message and vision for the country. Ofcourse in a democracy you cant necessarily pick who will follow you but that is why it would be important to pick the right people to begin with.
3. Craft a strong issue based, national message, Sell the message: He has a good grasp of issues, policies and the effect they have on the populace at large. Together with his team, he can refine his ideas and craft them into something marketable to Kenyans from all corners of the country. Firstly he has to sell the vision to his team, make sure they are really on board, really believe in the message, then send out the team to start spreading that message. Each region will have the message tailor-made to appeal to them but by and large it will be a national message. Part of the remit of this will include educating the populace about what the effects of certain things are (bad policies, vote selling etc).
4. Go grassroots, stay on message: Have his team out there selling him at the grassroots. Make periodic visits to all areas to meet and connect with the people.
5. Use technology: To keep in contact with the team, to keep his finger on the pulse, to help get his message out there and for fundraising.
6. Start now....but start under the radar: Start building his team now. Start finding like minded individuals across the country, approach them, sell them his vision, get them onboard. Get them really believing and then get them out there slowly recruiting more like minded folks. The next year or two should be spent quietly building his team and network (people and funds). By mid 2011 or so, he should aim to have a strong national network and a good fundraising mechanism, ready for the beginning of active campaigning.
Some points are repetitive and I'm sure there's some things I've missed out but that's what I could think of off the top of my head.
In my view, the current environment in Kenya presents a good opportunity for a new face who can get out there and galvanise Kenyans (specifically the youth) around them. It's still early but if we have such an individual he/she needs to start planning and working towards it now.