We explore energy scales, features in the normal state transport, relevant interactions and constraints for the pairing mechanisms in the high-Tc cuprates and Fe-pnictides. Based on this analysis we attempt to identify a number of attributes of superconductors with a higher T_c. Expanded version of the article published in Nature Physics, 7, 271 (2011).Comment: 6 pp, 4 figures, 1 table. Expanded version of Nature Physics, 7, 273 (2011
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