Thank God I am not in charge, I do not have privileged information, so my guess is as good as yours.
Based on what I know, I would start with the obvious, first I would close the borders for 90 days. I would revoke all visas, except those issued for humanitarian aid or political refuge. Once the Clinton legacy was cleaned up I would be better able to see what should next be done. I would not sell out the American public with unconstitutional anti-terrorist laws to appease the left wing. I would not curtail American liberty to cover for past administration mistakes. If I was President Bush I not jeopardize my reelection by squashing innocent citizens freedoms.
Even those need to be closely considered. Many of the algerian terrorists residing in Canada took advantage of that country's extremely lax refugee rules. Once they are in the country, they simply acquire an alternate identity using new documents and they are home free.