In response to Dave Krall's question about staining poplar, when
staining poplar or most any other wood I use a conditioner which
partially seals the grain resulting in a more even stain penetration.
Poplar really shows the difference between light and dark areas,
especially when using a dark stain.
Minwax and others make a conditioner but I've used a mixture of
polyurethane and mineral spirits with good results. Mix using a ratio
of about 1 part urethane to 3 parts mineral spirits.
If there's a big difference in grain color I sometimes apply two
coats of conditioner, letting each coat dry thoroughly before staining.
This also raises the grain which can be sanded before staining. Use
a tack cloth to remove any sanding dust before staining. Aniline dye
should work okay with this method. As all wood is different, try it
first on a test piece. Hope this helps.