In this paper, we analyze the outage behavior of decode-and-forward (DF) relaying in the context of selective two-way cooperative systems. First, a new relay selection metric is proposed to take into consideration both transmission rates and instantaneous link conditions between cooperating nodes. Afterward, the outage probability of the proposed system is derived for Nakagami- $m$ fading channels in the case when perfect channel state information (CSI) is available and then extended to the more realistic scenario where the available CSI is outdated due to fast fading. New expressions for the outage probability are obtained, and the impact of imperfect CSI on the performance is evaluated. Illustrative numerical results, Monte Carlo simulations, and comparisons with similar approaches are presented to assess the accuracy of our analytical derivations and confirm the performance gain of the proposed scheme.