look for straight sights. check the front for leaning off vertical and a windage drum that is near the center of the sight ears. check the rear for excessive run off to the side. both can be corrected easily enough...but, hey! it's a new rifle. hand pick a good one and avoid the extra work.

check for a reasonable finish on the wood and metal. keep in mind that the sar series is crudely finished, at best. you are merely looking to get one with an acceptable surface finish.
favor the finish of the metal over the wood. furniture can be replaced or refinished more easily than the metal.

be prepared to toss the oem trigger group in the trash and buy a redstararms group. not only will the exchange of parts eliminate trigger slap, but your shooting accuracy will improve due to a more calm shot release. trust me on this one...you will thank yourself for following this last bit of advice in the months to come.

good luck and shoot safely!