There is an interesting Halacha which says that from a half hour before the lighting of the Menorah, it would be forbidden to start certain things that might come to take your concentration and cause you to miss lighting at the proper time. We said that the best time to light is at Tzet HaKochavim which is about 12-12.5 minutes after sunset. (See the Daily Halacha entitled "Chanukah- Should A Wife Light The Menorah At The Proper Time Rather Than Waiting For The Husband Who Will Come Home Later.") So one must be careful not to get involved in certain things before Tzet HaKochavim that might lead him to miss the proper lighting.
First, one should not sit down to a meal within a half hour before the time for lighting. A meal (Seuda) would mean having more than a Kabetza of a bread, which would be about 2 ounces. A person may have a late afternoon snack if he wants, but he should not sit down to eat an official meal. He might get caught up in the meal and miss the proper time to light. If he asks from his friend to remind him to light, he may even a Seuda of Kebetza of bread, because his friend will remind him. (Torat HaMoadim page 139.)
Second, Halacha brings down in the Machatzit HaShekel written by Rav Shmuel ben Natan Neta HaLevi (1738-1827) that one should not sit down to learn within a half hour before the time of the lighting. Now of course it is permissible to check a Halacha or seek a quick reference, but to sit down and begin a Shiur would not be acceptable. This is because people become enamored in their study once they sit down and begin a lesson in Torah. However the opinion of Chacham Ovadia Yoseph in Hazon Obadya Helek 2, page 25, is that one may learn up until the lighting, but once the time of the lighting comes he should not sit down to learn. He does not forbid learning from ˝ hour before. That is the Halacha. See Torat HaMoadim page 139.)
Third, it is also forbidden to begin a Melacha in the house within the 30 minutes of Menorah Lighting. Here too are we concerned that a person may become involved in his task and miss the opportunity to make the Mitzvah of lighting at the proper time.
So again, within a half hour before Menorah lighting, one should not sit down to eat 2 ounces or more of bread, or do a Melacha in and around the house. And at the time of lighting one should not sit down to learn.
** Many Halachot on the Holiday of Chanukah are available by visiting www.dailyhalacha.com, and looking towards the right of the home page.
