(Assuming you have a time machine and want to take a vacation or Holiday break there.)
1. How to speak Old English. You are unlikely to find anyone who speaks other languages.
2. The laws of the Kingdom. Breaking even minor laws had large consequences.
3. How to get from place to place. You would find very, very few maps around.
4. The Saxon rules of hospitality. You may ask for a lot as a guest, but there were limits and bad consequences for going over the limits.
5. Riddles, songs, or a craft trade. The only travelers were bards with songs and riddles or coopers, tinkers, cobblers, etc. Any other type of wanderer was considered untrustworthy.