I believe having a good consulate in the sending country that's willing to work with the Canadian government.... We ran into an issue recently where it seemed like consular staff didn't like the temporary foreign workers we had chosen at the time. They delayed the visas for an excuse that was not valid, but by the time we were able to have it reviewed, we were well into the season.
I believe having some understanding among consular staff about the need to get temporary foreign workers to Canada in a timely fashion is vitally important. That, in particular, happened during a shortage here.