Well, we're given some clues throughout Scripture.
1. We have the description of the Holy City, right down to its size and the jewels and materials crafted into its gates and walls and streets (Rev 21:9-21). I'd post it here but it's a long passage.
2. We know that there will be a new earth, too! (Rev: 21:1)
Then I saw “a new heaven and a new earth,” for the first heaven and the first earth had passed away, and there was no longer any sea.
3. I think it's really curious that the sea/ocean will not exist anymore, if you take this verse literally. There may no longer be a sun or moon, though this verse doesn't specifically say that, only that they won't be needed to light the city: (Rev 21:23)
The city does not need the sun or the moon to shine on it, for the glory of God gives it light, and the Lamb is its lamp.
I also get far more excited at the idea of a new earth than I do about the Holy City, because I love nature and wildlife and solitude. And the thought of having a whole new planet to explore and enjoy, without any of the curses of sin (thorns, stinging insects, dangerous wild animals, sunburn) just sounds so wonderful! And even more wonderful is that we'll be communing with the Lord the whole time. Even if I'm wandering over some far-off mountain, I'll never feel alone or away from God.
4. We also know that there will be feasting and drinking in Heaven! Woohoo! (Matthew 8:11)
I say to you that many will come from the east and the west, and will take their places at the feast with Abraham, Isaac and Jacob in the kingdom of heaven.
5. No one will be married or get married. There won't be any need for it. All of our longings for love and companionship and intimacy will be fulfilled. (Matthew 22:30)
At the resurrection people will neither marry nor be given in marriage; they will be like the angels in heaven.
6. While we are assured that our earthly lives will be but a distant memory, and all of our tears will be wiped away by Jesus Himself, I don't think we're going to lose our personalities in Heaven, or that we'll become some conglomerate, Borg-like mass of consciousness. There are several verses where individuals are named after they've died and gone to Heaven (Matthew 17:2-4)
There he was transfigured before them. His face shone like the sun, and his clothes became as white as the light. 3 Just then there appeared before them Moses and Elijah, talking with Jesus. 4 Peter said to Jesus, “Lord, it is good for us to be here. If you wish, I will put up three shelters—one for you, one for Moses and one for Elijah.” And I'm honestly glad about this one, because the thought that I'll somehow FORGET who I am, or not be MYSELF anymore, is terrifying to me.
7. We won't be idle! The long-sustained image of people just sitting or standing around, smiling and doing nothing but singing, for endless millenia...does not sound appealing to me! We know that at least some Christians (this verse seems to indicate only those who endured the last tribulation and died for their faith) are going to reign with God (Rev 20: 4-6). Reigning is work! And if we think back to the Garden of Eden, Adam and Eve weren't idle. They tended the garden and the animals. The work was
pleasant, though. Not back-breaking, sweaty labor, but rewarding, enjoyable, useful work, as God intended it to be. I imagine there will be endless things for us to do, whether it be a role we're given or a choice we can make ourselves. I like to imagine that the Holy City has vast, vast libraries, where all the answers to all the mysteries of the universe can be researched. And even if you study for ten thousand years, there will always be more to study!
8. The last one that comes to mind is that...whatever is most delightful and pleasurable for us, will be ours, forever. This remains very vague, perhaps because what delights one soul may not delight another. Sounds pretty nice to me
(Psalm 16:11)
You make known to me the path of life; you will fill me with joy in your presence, with eternal pleasures at your right hand.