Reclaimed Wood Furniture

We have an old barn falling apart in the backyard. I've pulled about 35 boards off, which is about all that are worth having. I am working on resanding years of paint decay and dirt off and have already picked out a stain. My questions are this, is there any kind of pretreatement you guys would advise before staining and what kind of post sealent should I use. Also should I fill in the holes in the wood to lengthen longevity. I'm building two tables, one for indoors, one out. Two ladders to hang on the wall as book shelves. One head board and one coffee table. Lastly on wall decoration.

That is Mrs Va in the shorts, plus I am not sure why it flipped the one pic but the chain is supposed to be a W.