Thanks very much!
Hello, Craig! What a great question! I agree that it doesn't always seem obvious - sometimes I feel like it would be so much easier if God had just made a checklist of "do's and do not's". Let me give you 2 answers: a direct answer, and a short answer.
The Direct Answer: Some commands - such as the laws you mentioned (clean and unclean meats + the Sabbath) - were established before the "Old Covenant" and have been in place since the beginning of mankind. For clean and unclean meats, remember early on that God made a distinction between the two in the story of Noah in Genesis 7? The weekly Sabbath, of course, was established at creation in Genesis 2:2-3.
The Short Answer: Commands are given to people (or specific groups of people) at a specific times, for specific purposes. When studying specific commands, it's important to look at the Bible in its entirety and not zoom-in too closely on any one command.
So, what laws still apply to us today? Gary Petty gave 2 sermons which should thoroughly answer your question:
Enjoy your study!!