If you are a laborer, and especially if you are Hispanic (we have country-based quotas) it is, effectively, impossible to get here legally, unless you happen to have a relative, and then its LONG waiting period.
There's a very simple way to reduce illegal immigration. Its called more legal immigration . . . or at least a work-visa system.
They WILL keep coming. This is where the jobs are, this is their chance to make a better life. For many of them its their chance to live in a free country. And most of them are coming for that reason, not because they want our benefits. As long as we are rich and we have a long border with a poor country that borders on yet more poor countries, they will come. We should probably be flattered. But you will never solve the problem by hunting down strawberry pickers, maids, and construction workers . . . because there will always be more.
Frankly, anyone willing to walk across the Sonora desert to get here, likely in the company of a vicious Coyote, and pay thousands for the "pleasure" of doing so is not going to give up and go home. And if they get sent home, they'll probably come back.
Until we give them a legal way to come, or until Mexico gets its act together, they will come here illegally.