In this paper I have given an overview of algorithms for tactical generation within unification based formalisms. I have argued that head driven bottom-up generators are useful for two reasons. First the order of processing is geared towards the semantic content of the input and the information in the lexicon. This results in goal-directed algorithms with reasonable performance in practice. Second this order of processing puts less restrictions on grammars than top-down generators and Shieber's chart-based bottom-up generator. Especially for grammars written in the spirit of lexical, sign-based linguistic theories head driven bottom-up generators are useful.