In toluene nitration, which positions are favored and why?

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The main idea here is how alkyl substituents direct electrophilic aromatic substitution. A methyl group on a benzene ring donates electron density to the ring mainly by hyperconjugation (plus a small inductive effect), which activates the ortho and para positions toward attack by the nitronium ion during nitration. That’s why nitration of toluene occurs predominantly at those two sites rather than meta. Among the activated sites, the para position is less hindered by the methyl group than the ortho positions, so the para-substituted nitro product forms in greater amount. Meta is not favored because the methyl group does not stabilize the arenium ion intermediate at meta as it does at ortho and para. So, ortho and para are favored, with the para product typically being the major one due to reduced steric hindrance.