The best solution is a whole house transfer switch. It will transfer the source of power from your utility company to your generator. By it's very nature it isolates the lines and no generator power will back feed to the utility company wires. It's available in manual or automatic models. It needs to be rated the same or greater than the service it feeds. In your case 200 amp. It will be expensive, often a significant percentage of a generator's cost. There are alternates.
One is to re-wire selected circuits in your home to a smaller distribution panel. Then this smaller distribution panel has the transfer switch, manual or automatic. It's lower cost because the switchgear rating can now be reduced to the rating of the generator. Selecting what circuits to re-wire and actually doing it are often difficult. Usually the existing wires are two short. Lengthening them in a way that meets electrical code is possible but needs space and is labor intensive.
A second method is to back feed the generator. This is possible and still meet the electrical code. It depends on a mechanical lock out of your existing main distribution panel circuit breaker with the backfeed switch or breaker from your generator. The objective is to prevent any possible generator power from being fed back to the utility companies wires. This can be accomplished with products like the Kirk key. See:http://www.kirkkey.com/default.aspx?Page=Products
You will have to engineer the lock out system to your needs. The basic idea is to use electric Solenoid Controlled Interlocks to prevent the house main circuit breaker switch from being on whenever the generator is running. Download: http://www.kirkkey.com/default.aspx?Pag ... %20Schemes
and look at scheme 35A. Systems using the Kirk Key are commonplace in industrial switchgear.
My guess the backfeed method with Kirk Key lockout will be the least expensive. Of course it's a manual only transfer method.
My 15 KW water cooled diesel generator has a 1 KW electric coolant heater. I normally turn it on only when I'm expecting bad weather. For other times I added a glow plug controller. I don't regularly start my generator for testing purposes. The starting battery is continuously charged with a high end microprocessor controlled battery charger. The fuel needs anti-bacterial treatment.