More good than what? You've only named one option: buying other example.tld domains and redirecting to your existing .com. What are the other options you're considering?
Possible questions: --would buying other domains and redirecting to .com put you in a worse position than before? --under what circumstances would some other tld be better than .com for the primary? (The one that gets cited a lot is a country tld if you've got a non-US regional emphasis.) --if you're redirecting, what form of redirect is appropriate? (For comparison purposes: I own a .com that I registered purely to keep the dragons from getting their hands on it. It redirects to a .ca which I don't own. When I was working out the redirect, I thought of at least six different ways to do it.)
sorry I'll try to explain what i want. I have [keyword].com and If i'll buy [keyword].org/net and redirect it to [keyword].com will it effect on search position in [keyword] ? :D or is there other better way to do anything with the other domains on org and net ? :) (when i write [keyword] it means that web-site adress is main keyword)
makiaveli... thanks for a more thorough response. It makes answering questions easier.
If [keyword].org/net have not been previously promoted, then IMO the keywords in the domain names are not going to boost your search position.
Owning and redirecting those domains will, though, prevent others from using them... and it's something I recommend that clients do.
If [keyword].org/net have been previously owned and promoted, though, the situation gets a bit trickier, as 301s may be redirected their inbound link credits as well as their liabilities... and those may include keyword linking effects. Some people buy active domains for this purpose.
My own approach, much more conservative, is to let previous link credits expire before using a domain.