Dharma Contemplation was developed to provide a means for deep investigation of early Buddhist texts, particularly the early discourses of the Buddha.
Other texts have been used for Dharma Contemplation, but care should be given to the wisdom content if one wishes to maintain the purpose and intention of the practice.
Brief excerpts are recommended. A short paragraph, or even a sentence or two, can work well. Excerpts longer than 200 words will be difficult to absorb and thoroughly engage within this practice. While technical teachings, like lists of mental factors or causal sequences can be useful, teachings with strong imagery, similes, or metaphors have proven to be particularly powerful. When excerpting texts, attend to the imagery or cultural references that may be problematic for some practitioners. If you decide to insert gender-neutral language, this should be done transparently so as to retain access to the original text.
Translations of early Buddhist texts are available from a number of sources including online at Sutta Central and Access to Insight.