Here are my thoughts on guidelines for placement of objectives in a competitive tournament environment. Like I said these are my ideas, I don't expect anyone to agree with them.
1) Objectives should be spaced apart by 12" or more.
2) Objectives should be at least 6" from any table edge.
3) Objectives should be placed on the ground level.
So those are my three simple guidelines. I think they are fair in that they don't give an advantage to any particular style of army. My opinion it's gaming the system when a player places an objective on level 2 or higher in a building or a ruin. The reason I feel as such is that some units cannot climb up above any level over ground level... Beasts, bikes and cavalry all have these restrictions. If there are multiple objectives (4 or more) it's not as big a deal to me but often I have seen Space Marines and IG place an objective on a third level or higher in their deployment zone. So you will have to clear out the immediate area then climb up two or more floors. Space Marines can take a Tech Marine and fortify cover, as such versus a biker army it is impossible for an opponent to take that objective and extremely difficult for them to shoot the enemy off of it. So that is one valid reason in my opinion for the suggestions I have made above. It's unfair to me and boring to play any game where you can at best hope to eek out a draw.