Due to several contacts we've received from users confused as to how the summoning feature works in game, we have provided this list to help. 

Conditions for summoning (White Sign Soapstone):

1. The host (person who's game world will be used) must be human. The client (person joining the game) can either be human or undead.
2. 
   
3. The client’s level must fall within 10% (above or below) of the host’s level. Generally, this example formula should give you a good idea on whether you will be able to join:   (L_C x 1.1) ≥ L_H ≥ (L_C x 0.9), where is L_C the level of the client and L_H is the level of the host. For example, if the level of the host is 20, then they will only be able to summon players who are levels 18 to 22.
4. 
   
5. The area boss (Taurus Demon, Bell Gargoyles, Moonlight Butterfly, etc…) in the host’s world must still be alive. A client can still be summoned even if the client has already defeated their own area boss.
6. 
   
7. The host must not have placed down a summoning sign. Summoning signs from other players will not appear in a host’s world if the host also has placed a summoning sign down. This is to prevent a network conflict of the host joining someone else's game world while the clients are trying to join the host's game world.
8. 
   
9. After successfully summoning, the client will return to their world if the area boss is defeated, the client is killed or the host is killed.

this means you can be on a server with very few to know ppl at all! if your unlucky

and they have restricted the level range greatly...all these work toghether to pretty guarentee Dark Souls will be a COMPLETE single player game

The level restrictions aren't that much different from Demon's Souls, since the formula is Host Soul Level +/- (Host Soul Level *0,1) + 10. At higher Soul Levels you we're pretty restricted with what people you could play against, that's why Soul Sucking became a very common thing to do, with a lot of over 200 SL players letting themselves being Soul Sucked to starting levels.

Quite frankly, the entire summoning system is almost stricly similar to Demon's Souls, except for the multiple servers/lobbies, which make sense since Demon's Souls had separate servers for each version and Dark Souls is supposed to add players from every part of the world into the various servers. As for the chance of you playing on a lobby with no people, that could happen, but as time goes along and more people buy the game and play online, that becomes a lower and lower possibility. Then again, as you go up in levels the chance that you encounter someone close to your levels also decreases, just like in Demon's Souls.

Don't know why the online system in Dark Souls is getting bitched at. It seems as if people didn't play Demon's Souls or had forgotten how it was.

huh demons let you play with whoever without mjultiple servers?( unlesss u mean american which suffered from the same thing ctually)

. in demons after level one 100 they actual increased the restriction( i was 100 and makinmusic was like 121 waaaay more than a 10 difference) we both played with super high leveled ppl..the restriction makes it harder to find ppl in your range at the some spot in time.

mutiple servers seperates eveybody .. like ive played the game so far not being summoned or being able summon..no blk phantoms, .thats bad those are crucial features to this series ..and we shouldnt be going this long without encountering them.

Yes I did have the american version and yes I did suffer from the same multiple servers/lobbies restrictions. The european version had the same issues if i'm not mistaken, only the Asian version was one big server.

No they didn't increase the restriction after level 100, it's the same formula for all levels, you just get more levels as 10% of 100 is 10 + 10 = 20. When I was SL 206 before I stopped playing DS, I had an extremely hard time not only finding other people to invade but also summoning or being summoned. Even if the gap for 206 was 31 levels +/-. And btw, who summoned who when you played MakingMusic? Because your level fell in the range of MM's level restrictions (121 +/- 22)

Like I said, as the game gets more players, you'll start getting the servers and lobbies with more people. I've seen plenty of videos online with people invading, helping and summoning, so you might just be having a bit of a bad streak of luck in regards to finding other players. 

Isn't the SL cap for Dark Souls like 140 or something? That would mean it's easier to hit the cap than in Demon's Souls, which was 712.

Also, apart from the multiple servers, everything seems pretty much the same as Demon's Souls.

This was rumoured because the characters from the From Software team that invaded players who acquired early copies of the game all had their builds at level 145. It's not confirmed though.

or they could just cut the multiple lobbies( or make them bigger) and offer the true xxperienece like teh director wanted.

you seem to want to settle for the as of now broken online,..i guess becuase you got used to it in american demons souls.. the asia version had a seriously active fanbase..u put a soul sigh down.you were summoned in like minute..blk phantoms invade at every oppurtunity..I want that back. dont let love for something allow you to settle for less

Darks Souls completely dead .. ieft my soul sign down for almost 30mins..not once was i summoned

not seen one blk phantom

very few bloodsplurts

I know they seem small but just these 2 things workin with eacjhother seriously reduces the online activity..its bad enough they have multiplr servers but to also restrict the level difference sucks to..they should of done none..or 1 the other- multiple sservers higher level restriction or  1 server but tighter level restrcitons..<---- one of  those 2 would of worked just fine but both is to much.

they have to fix  the servers to return life back in into this dead world ...which is kinda ironic since the world is dead but..

You get me wrong. I don't mind playing Dark Souls in a whole big server where you could find pretty much everyone you wanted to play with and I would welcome that improvement over Demon's Souls. What I'm saying is that I don't understand why the online component suddendly became an issue when it was widely praised on Demon's Souls. Improvements would be welcome but I like the system as it is.

And again, here are some videos of people playing PvP and Co-op summoning: http://www.youtube.com/watch?v=wumI_I4jeTM, http://www.youtube.com/watch?v=yeoy_NGiJkc&feature=related, http://www.youtube.com/watch?v=qkeMLdjrdP8&feature=related.

Just because you're having issues finding someone doesn't necessarily means that it's the same for everyone else. I had entire sessions on Demon's Souls, even on low levels where I couldn't find anyone (took me ages to finally get the Old Monk's Head Wrap because of that) and then there were sessions were I was invaded and could invade almost constantly. 

So basically it's exactly the same as demon souls on the PS3 then.