We study features in the optically detected magnetic resonance (ODMR) signals associated with negatively charged nitrogen-vacancy (NV${}^{\ensuremath{-}}$) centers coupled to other paramagnetic impurities in diamond. Our results are important for understanding ODMR line shapes and for optimization of devices based on NV${}^{\ensuremath{-}}$ centers. We determine the origins of several side features to the unperturbed NV${}^{\ensuremath{-}}$ magnetic resonance by studying their magnetic field and microwave power dependences. Side resonances separated by around 130 MHz are due to hyperfine coupling between NV${}^{\ensuremath{-}}$ centers and nearest-neighbor ${}^{13}$C nuclear spins. Side resonances separated by approximately ${40,\phantom{\rule{0.16em}{0ex}}260,\phantom{\rule{0.16em}{0ex}}300}$ MHz are found to originate from simultaneous spin flipping of NV${}^{\ensuremath{-}}$ centers and single substitutional nitrogen atoms. All results are in agreement with the presented theoretical calculations.