Going to first session I'm pretty new to buddhism, I come from a christian family and as such I attended church for the earlier part of my life.

I'm wondering what to expect from my first session in comparison to that of church.

I'm also asking if there's any general advice/tips you can give me for my first time.
At a Theravada monastery:


You have to be familiar with taking refuge in the Triple Gem and taking of the five precepts:
http://refuge.sirimangalo.org/
Remove shoes and hats when you enter the monastery.
Wear conservative clothing. White color clothes are more appropreate.
Avoid shouting, idle chatter and laughter(can smile when appropriate) while you are there
Avoid running. Walk quietly.
While listening to Dhamma talks or meditating with others, turn off your phone or keep it in silent mode. If you need to answer an urgent call or text, quietly go outside the room.
If you make an offering to the Buddha or the Sangha, do it using both hands and bow afterwards.
If you offer food, do it well before noon as monks cannot accept food after noon. Make sure the food is prepared for consumption as monks are not allowed to cook food.
Do not offer food that is already consumed by another.
When offering food to monks, don't place it on the table expecting them to take, like in restaurants. You must personally serve every curry into the bowl or plate. If they don't prefer a certain dish, they will indicate by covering the bowl with hand as you try to serve.
Don't consume food while attending meditation sessions or listening to Dhamma talks. 
Don't smoke inside the monastery.
If a monk is standing and addressing you, don't be seated. If a monk is seated on a couch/bench, do not sit on the same at the same time. Sit on the floor or sit on a chair which is lower and less luxurious. Do not sit directly facing a monk or a Buddha statue. Sit to the side. When sitting(chair), do not put one leg over the other or sit with your legs wide open or stretched  infront.
Do not address the monks by name. Use respectful terms like 'Bhante', "venerable sir" etc.
Do not try to shake hands with the monks, pat on the back etc. Avoid all unnecessary physical contact within the monastery.
Do not take selfies with Buddha statues or monks. Do not take pictures with your back turned to the Buddha statues.
Do not try to practice your own method in the monastery. Follow the instructions by the teacher.
If you wish to make a donation, don't hand money to the monks as they are not allowed to handle money. Instead, look for the donation box or ask them how to make a donation.