There are always questions about 'how early (or late) is too early (or late)' to show up when invited to someone's home...
Certainly, you do not want to arrive late to someone's home, but you also don't want to arrive more than 5 minutes early, either. In many cases, your host may still be running around finishing last touches. You may think you're being helpful by arriving early, but in reality, your host will now have to take away from his/her final duties in order to 'entertain' you.
Upon arrival, remove your shoes or, at the very least, wipe your feet well. In addition, your feet should remain on the floor (instead of on a table, underneath you on a couch, etc.). While it's great that you feel at home, this particular home belongs to someone else!
When your visit includes a meal, wait until your host takes his/her first bite before beginning to eat yourself, and try to eat each course in pace with the others at your table.
If you have life-threatening food allergies, of course let your host know in advance, but do not expect special food to be served...instead, try to eat what you can and leave the rest (imagine if you hosted an event for 20 people, and 10 of them all requested 'something special'). A good host will do what he/she can to take care of all guests.
After the meal, or at the end of your visit, offer to help clean up, but do not force it. It may be easier for your host to take care of things him/herself.
Finally, do not overstay your welcome. A good host won't throw you out, but if your host makes mention of having to get up early or feeling tired, that's a good signal that it's time to bid good-night!