I think any positive action one does for his/her country is the best way. The ultimate way is to join the defense forces, but it's not for everyone, and there may be many patriotic people who cannot take this action. The country is what its people are.
Interesting question - I think it is dangerous to be overly patriotic as we are all part of the multi-cultural human family. A little bit of pride in the nation is fine but taking patriotism to the point of exclusion is not acceptable for me.