Okay ... you're in love and want to spend as much time together as possible. Got it.
It is most important to live together before considering the 'M" word - Marriage. If you're lucky, you live in an area where living together is acceptable. If you're young you know that most relationship that start in the 20's don't last, for different reasons, as people change and grow through the years and seek passion at any age.
Here are a few things from CNN to consider...
1. Agree on who will pay for what.
2. Agree on how to handle an unplanned pregnancy.
3. Decide if they're both on the same page when it comes to marriage (in general, and to each other).
4. Come up with at least one reason to move in together other than finances and convenience.
5. Consider some of the realistic challenges cohabitation might create.
6. Meet each other's close friends and family members.
7. Know each other's financial situation.
8. Agree on a three-year plan.
9. Say "I love you" to each other.
10. Decide whose bed you're going to keep.
11. Spend more than two nights in a row together.
12. Experience heartbreak on some level.
13. Celebrate at least one major holiday together.
14. Discuss how to divvy household chores.
15. Pick out at least one new object of some value -- financial, aesthetic, or symbolic -- for the home together.
16. Have a trial sleepover for your pets.
17. Travel together.
18. Make sure there's enough closet space for both of you.
Illegal alien looking for a green card. Illegal alien waiting for their space ship to return...
Birth control: Honesty is the best policy - don't get trapped especially if you don't believe in abortion.
Generally there's no good or bad with sex unless one person can't perform - now that sucks. It is always about compatible for the couple and the need to get to the point.
Make a list of all things that make you compatible ... or not
Try spending a few days together that are not a vacation
Music likes and dislikes
Sleeping patterns - snoring is a huge issue
Need for privacy ... now lost
Discuss pets and the care of them
Discuss school and career goals
Find out hidden secrets that could and probably will affect the relationship, but don't get paranoid. For example, can the other person remain monogamous - not easy in today's world.
See a therapist if needed
Know if the other person has a personality disorder and won't get help. Don't keep telling them they're crazy. Can they be violent?
Substance abuse - generally a means of self-medication and not great to cope with. You will get hurt and wonder where all the love and passion went.
If your relationship is what I call the 'sine wave effect' - you're together -> you split up -> you're together -> you split over and over, let it go.
Do not accept abuse
You need to be friends and respect each other before living together because the pressures of everyday life will sweep over you like a giant tsunami
Take your time. It is often best to try living together a week at a time and see how it goes.
Be practical in how long you might stay together
Always have a way out if it doesn't work out - the same goes for the person who you are living with. They may not have resources to move on ... collateral damage ...they also owe you money. Will they pay you back? Most likely not.
Do a comparison astrological chart.
Consult a psychic - but don't keep looking until you find one who says it will all work out.
For fun ... Use I Ching or another Oracle of Divination.
Trust your dreams more than synchronicities which can lead you in the wrong direction.
Understand the karma you share - perhaps seen as soul mates in this reality. Never rationalize that they are abusing you now because you abused them in another lifetime. That is so lame!
Try a past life regression alone or together 'for fun'.
Above all trust your instincts and know your psychological profile as it regards relationship. They are not for everyone.
Is all of the above common sense? Of course it is. But follow the lists anyway. Good luck!