This thesis presents three chapters. In Chapter 1, I propose a simple one-to-one matching model, where individuals on one side have private information that affects the preferences of the individuals on the other side. I show the existence of the stable and strategy-proof mechanism in this environment. I present an algorithm that defines this mechanism - the Serial Dictatorship algorithm with cutoffs. I also consider the concept of obvious strategy-proofness. I first consider the case where only preferences, but not experience levels, are sellers' private information. For this case, Serial Dictatorship with cutoffs elicits preferences in an obviously strategy-proof way. On the other hand, when only experience levels, but not preferences are private information, I show that there is no obviously strategy-proof and stable mechanism. A consequence of the latter result is that obvious strategy-proofness is incompatible with stability. Chapter 2 considers settings with rich private information - an agent's type may include private information other than just his preferences. In such settings, I identify a necessary condition for obviously strategy-proof implementation of social choice rules. I consider applications to strict preferences, matching and object allocation. The main assumption behind the obvious dominance is that agents might be cognitively limited and can not engage in contingent reasoning at all. This assumption is unreasonably weak compared to the standard assumption that agents can perfectly distinguish contingencies. In Chapter 3, I strengthen it slightly by assuming that agents are able to do at least some contingent reasoning. I define what it means for the strategy to be obviously dominant with respect to a partition of the state space. I call such strategies partition dominant strategies. A strategy is an almost obviously dominant if, for all possible partitions, but not for the coarsest, it can be identified as being partition dominant. My hypothesis is that even though some agents can not do state-by-state reasoning as rational players do, they are able to do at least some partitioning of the other player’s actions and regardless of how the partitioning is done, the agents can identify an almost obviously dominant strategy.