From DB's comment thread:
1) Make it easier for legals to come into this country by restructing our visa system to let more workers into the country.
2) Crack down hard on companies that use illegal workers.
3) Make illegal immigration a felony and subject to deportation.
4) Make a grace period where all illegals can come forward without penalty. They would then have a choice. They could join a guest worker program which would penalize them (fines) and make citizenship difficult. Or they could leave and come back at the back of the line and avoid the fine, but they would not be allowed to come back for a year.
People would have far less motivation to sneak into the US because they could mostly come in openly and they would have no place to work once they got here.
This program would put legal immigrants ahead of illegals, would allow us to document pretty much everyone who enters our country, and would allow qualified workers to find jobs here, which is good for the market.