This corpus-based study investigates the inter-relation between discourse markers (DMs) and other contextual signals that contribute to the interpretation of coherence relations. The objectives are three-fold: (i) to provide a comprehensive and systematic portrait of the syntax and semantics of a set of coherence relations in English; (ii) to draw a distinction between mere tendencies of co-occurrence and strong predictive signals; (iii) to identify factors that account for the variation of these signals, focusing on relation complexity, DM strength and genre preferences. The methodology combines systematic coding (description) and multivariate statistical modelling (prediction). While the effect of genre and relation complexity was found to be null or moderate, the presence of discourse signals systematically varies with the ambiguity of the DM in the relation: signals co-occur more with ambiguous DMs than with more informative ones.