A survey on some new results obtained in joint work with S. Mueller is given. In particular, we present an optimized 1-D-scheme (the optimal drift model) that is based on overlaying a given binomial scheme with an additional drift process and that obtains a higher than advanced schemes such as the Tian- or the Chang-Palmer approach. Further, we introduce the orthogonal decoupling approach to solve n-D-valuation problems. This approach is based on a non-linear transformation of the state space, always results in well-defined probabilities in the approximating n-D binomial tree, and admits a regular convergence behaviour.