Where are all the summoners in Anor Londo? I've been summoned two times in the last hour..
Level 28.
What I have found to be the best summoning levels and locations on first playthrough (I have tried to be specific enough without providing any spoilers):
1. First summonming in the game is undead Parish: Low levels - leave summoning sign either in the church (alter area) or courtyard before path to blacksmith if you want to help clear out the area. If you want to boss only leave summoning in front of boss door.
2. Capra Demon (Undead Burg) area (good for a wide range of levels in the beginning of the game). You will get great summoned success from level 15 to 35 as most people will be around level 20 or so when taking on this boss. Leave summon sign on bridge before boss door. If you want to help with level leave summoning sign on stairs leading down to area or on the street just after the dogs. (In all of my playthroughs I have only seen a couple of summon signs in these areas. Majority have been on bridge before boss).
3. The Depths - There is really not a lot of action in the upper areas of The Depths. Best place is the bonfire you get access to via the sewer key. This is a highly recommended area to spend a lot of time being summoned duing the first part of the game as not only is it a lot of fun, you also get a shit-load of souls if you many to help the summoner bag the boss. Level 25 and up to perhaps 50 to 60 will get you a lot of action. Best around SL 35 to 45. I have spent hours here as a sunbro and bascially got enough sunlight medals to complete the convenant.
4. Blighttown - Best place is in the swamp bonfire (although there is a bit of action in the first bonfire). SL 50 and up will get you a lot of action. This was my strategy while waiting for summons here: (Defeat this boss first allow access to Sens Fortress. Find the ring that helps with item discovery. You should also have the ring that helps with movement in the swamp - HINT back to Asylum). Once you have these go back to Blightown swamp and leave summons. Use rings mentioned above to help farm worms while waiting to be summoned. There is usually a lot of action here, but I have gone through periods when it can be a bit slow. Farming of worms about for ore will help pass the time.
5. Sens Fortress (SL 50 and above) Basically the only place with good action it in front of the boss door. Great place to use for a while as each time you are summoned all of your items are replenished and you can drop another summons without having to go back to bonfire.
6. Andor Londo (SL 55 and above) There are many good summon locations in this area. If you do not mind the possibility of helping people who have not activated the bridge place summon sign on the span of bridge where first gargolye is. (This is best location for higher action though) If you do not want to help people walk the rafters place summon sign on bridge span where 2nd gargolye is. You will most likely be helping people get by the archers though (this area is not as active as the first bridge span is). If you simply want to help with the boss, place summon sign at bonfire inside the castle or in front of boss door. This entire area is great for summons for SL 50 to 80.
Once you get the Lord Vessel you get help people in later parts of the game). Any SL above 70 will get you a lot of action. Action will start to slow down though as you get to higher levels. However, I still get a fair bit of summons at SL 120. At SL 130 I was getting lots of hits in the Painted World.
Recommended locations:
Dukes Archive: 1st bonfire you "find" after you loss to Seth (not the bonfire in the jail).
demon ruins : first bonfire you find after going through the hoard of Capra Demons.
Tomb of Giants: the last bonfire before the boss fight. Or right in front of the boss door while farming for humanity with baby skeletons.
Once you get to higher levels, the best way to play PVP is to join either the Forest Covenant or the Dark Brotherhood and start enjoying the game invading other people. Or go to the Kiln and enjoy some hardcore PVP although this area can be cheap as well.
Hope this helps as bit.