Which kind of link building is indexed quicker in google?

[websitebuildersperth]

Hi,
So, over the past few months I've been trying to come up with the answer of which form of backlinking is index quickest.
From what I can tell this is the order
1. Direct Link Exchange (not recommended)
2. Blog Commenting
3. Directories
4. Forum Linking

I don't know if that is correct but that is my experience, without pinging the link urls mind you, that's just on average from what I've experienced.
What you guys think or what have you experienced?
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