5 Things To Look For When Buying An Esrog: The Top Section is Crucial – Always start checking from the top, the side of the pitom or where the pitom would be. A black dot on the top that is easily noticeable renders the esrog pasul. A white dot would also invalidate the esrog, but most light colored dots are beige, not white. This is the most common problem to look for.
The Whole Body – Next, the entire esrog should be examined for holes or scratches that would make the esrog chaser, lacking. Also, numerous discolorations that can be seen from all sides while examining the esrog render it menumar, spotted, and pasul even if they are all only on the bottom of the esrog. Furthermore, brown spots may indicate a recent bruise which is likely to darken and turn black over the course of the next few days.
The Stem – The stem should be checked to make sure it is firmly attached and not likely to fall off.
The Pitom – The pitom should also be inspected to insure that it is free of blemishes and that it is strong enough to last the week of Sukkos. If the esrog does not have a pitom, the place where the pitom would usually be should be checked to verify that it did not break off, but rather grew without a pitom.
Overall Beauty – Of course it adds to the beauty of the esrog if it is a good size and has an attractive shape and color, but these are of secondary concern.

7 Things To Look For When Buying A Lulav.

Closed – The primary issue is to insure that the middle leaf is completely closed all the way to its tip. Preferably, one should not even be able to see two separate points.
Not Dry – Also, it is important that the lulav has not dried out and shriveled, but a little brown on the tip is natural.
Complete – Furthermore, care must be taken that the tip has not broken off.
Covered In Brown – Some prefer to take a lulav where the tip is covered with brown korah insuring its complete closure, while others avoid such a lulav out of concern for what lies underneath.
Knepel – Also, some prefer a knepel, where the tip of the leaf is folded over, as such a lulav will almost never split. However, some poskim invalidate such a lulav because of its bent state.
Shape – A lulav that bends slightly but not so much that the tip points back to the bottom of the lulav is not a problem and has all the advantages.
Beauty – A long, thick, straight and green lulav is ideal, but not of primary importance.

4 Things To Look For When Buying Aravos

Edges – The aravos should have long leaves that are either completely smooth or only have very fine serrations.
Lavluv – One should check that the tip of the branch has not broken, and for this reason many look for aravos with lavluv, the bunch of immature, unopened leaves at the tip.
Dried/Shriveled – Also, the aravos should not be dry or shriveled and no leaves should have fallen off, and since this is a very common problem, it is preferable to replace the aravos frequently over the course on Sukkos.
Grey Goods – Finally, since aravos are commonly grown in private yards and on public property, it is especially important to insure that the person you are buying from really has permission to cut and sell them. All of the arba minim are pasul if stolen

5 Things To Look For When Buying Hadassim

Mishulash – The main concern with hadassim is that the leaves should be in sets of three. This requires examining that all the sets of three leaves in the required length grow parellel to each other.
Falling Leaves – Furthermore, one must check that no leaves have fallen off.
Dry or Broken – Also with hadassim, they must not be dryed out or broken at the tip of the branch.
Size – Preferrably, the leaves should each be smaller that a thumbnail
Branch Exposure – Preferrably each set of leaves should be close enough to the next set that none of the wood of the branch is exposed. Revach.

Important Note: It is important and customary that once you have your Arba Minim to show them to your Rav to make sure they are kosher.