Whenever you can, try to centralize inputs, channeling them into a main collector, for example the e-mail. This will allow you to be more systematic in your processing.
"Could you please send me an e-mail with that?" - this applies specially if the request gets you in a moment where collecting it is not really handy (e.g. driving, or at the coffee machine).
Many people also send e-mails to themselves, which can be really smart if that's your main processing channel.
In general, group as much as possible in one spot. Physically also: having an inbox is a must on your desk or at home. Even a special compartment on your briefcase can serve you well as a collector.
This applies to having different email accounts too right?
How many people have consolidated down to one email address or one personal and one work?
I have four email addresses that i use actively (one work and three personal), and through the course of the last 25 years have had numerous ones – think compuserve, aol, schools, different jobs, and different providers. My wife never quite knows what email address to email me at, and thinks this is all atypical.