Quests can be a little wonky. Note that trader-given quests can only be returned to that particular trader, but note-based quests (the little notes you find in loot saying "Hey







, we've been watching you..." etc.) can be returned to any trader (and they don't have a return-point marker on the map). I went to a trader once and turned in like 4 quests in a row and I had no idea where they all came from. I thought I just had one quest, but she kept giving me rewards. I guess I had a few note-based quests in the list. It's all visible in your quest list, but of course I wasn't really paying attention to that...
Liesel is correct about the orange bouncing exclamation point for any POI or trigger-event quest. Make sure you can see it before your partner triggers it (and vice versa). The dig up treasure quests have the locator icon in the compass - make sure you both see that. I think you can re-share quests any time up until the trigger is activated, or until the buried supply crate is opened.
BTW, If anyone has good tips for MP, let me know.
What's the best way to play MP?
Dedi, or just connect to my game?
How to minimize lag/teleporting for for the other player?
Can we share a land claim? (as in both pick up items in one land claim)
Assuming you don't have any underlying network issues, if you have a separate machine with enough spare CPU to run a dedicated server, that would be best since it offloads a bunch of the work to a different machine. It doesn't take a whole lot to run a dedicated server for just a couple of people. A Core i5 or i7 in the 3.0-3.4GHz range with 16GB RAM would be plenty. Probably even 8GB is enough. (Used corporate workstations with those specs can be had on eBay for $200-250.) [EDIT: oops I see you're in Estonia; probably the eBay comment doesn't apply so much to you.] My own server (also my main home PC) is a Core-i7 3.4GHz, 32GB machine with a Radeon 560 in it. It works great and can even run the client at the same time if I want. Server process takes 2-3GB of RAM and doesn't really stress the CPU(s) too much.
Our usual mode is me connecting via laptop (on my own LAN) and my co-op partner connecting from his house, direct to my IP. Works great. My internet connection gets about 160Mbps down and 10MBps up, so not fiber, but not too shabby. The server should probably be wired, not wireless. Client can go either way, though we found that voice chat through Steam was very weird when I was on wireless (my laptop). You need a solid wireless connection if you don't want garbled voice and stuttering/teleportation in the game. For a while I had to run a 50' patch cable from the nearest switch over to the desk with the laptop. I have since tossed my Linksys router in favor of dedicated wireless APs upstairs and downstairs (Ubiquiti Unifi stuff). Now I can play on wireless with no issue, with speeds nearly the same as I get from my wired PC.
I don't know if allies can pick up objects (workstations, etc.) within your land claim. We've never tried it. I'm sure someone here knows. I did allow two LCBs per player in our game, so I could allow workstation pick up in both our main base and our crafting base (aka the Screamer beacon). One of the benefits of running a dedicated server is all the fine-tuning you can do with serveradmin.xml. Lots of things in there are not available in the UI, or you at least have a wider range of options (want 47-minute days? Sure why not!).