Deep Sky Stacker (FREE) remains a one of the most popular pre-processing applications for Windows. Stacking and saving your data with these settings is essential to getting good results from StarTools.
When applying the important pre-processing do's and don'ts when using StarTools with any stacker, you will want to configure Deep Sky Stacker specifically in the following manner.
With all the above settings made, you can then safely stack and (assuming you used a DSLR or OSC) import your dataset into StarTools as "Linear, from OSC/DSLR with Bayer matrix and not white balanced".
If stacking multiple mono datasets for use in a composite, make sure to use one set's finished stack as a reference to stack the others with; StarTools's Compose module requires every dataset to be the same dimensions. Aligning remaining channels against an initial channel during stacking is particularly important to ensure consistency of point spread functions across channels; do not align finished stacks against each other after stacking.
Please consult the "Important dataset preparation do's and don'ts" section for further advice on improving your datasets.