http://www.fishlore.com/Forum/betta-...d-first.0.html
The above is a good place to start when looking for some basic information on the care of the betta.
As far as the tank mates, you can use a frog but be careful that it does not nibble the betta's fins as the betta will not see it as a threat usually and will just let it happen (unless you get a very aggressive betta in which case I have known of them killing the frogs). If you have fin nippers in either frogs or fish the betta is going to end up with a case of fin rot and lately fin rot has become much more tricky to treat. Poe is VERY correct that the other occupants of the tank should establish their territories first. It does not insure a docile betta but it helps sometimes. It is certainly more likely to cause a problem if the betta is given a chance to dominate the tank and then has company added.
The bettas that I have love the tall plants to sleep in, but they also like sword plants with wide leaves to rest on during the day. They do not like to have the tank so stuffed that they cannot swim around the leaves but they do like to have a lot of plants and places to explore; caves, and rocks and wood with little holes. Just be careful not to have things with really small holes as a betta will try to get into anything and they do not swim backwards so they either need a place with 2 holes big enough to go through so they have a way in and a way out or a place big enough for them to turn around when they get inside. 3" minimum inside I would say. They also like bridges and things they can swim under and around. Now you are not going to be able to get a lot into 5 gallons but choose a couple items for them to explore like your wood and some plants and maybe a small cave and they will love you. I saw a small octopus at Walmart that my Bettas love. It is very small but has several holes but they think they are hiding inside even though they are perfectly visible. Plants; you may want to try Anubias nana, Java Fern, Amazon Sword, Anubias petite, Java Moss (it is a mess but they LOVE it ~ it is like a big pillow for them ~ but they trail it all over the place. If you want a neat tank do not get it.) These are all low light plants that are easy to grow. They will be easy to purchase too if you find a place that carries plants they should have these as they are the common ones. They are also good at keeping nitrates down.
It sounds like your set-up is going to be good and you have given it much thought. I would not get a snail if your objective is to clean the tank. Snails are large waste producers and will add more dirt than they will clean up. If you are wanting algae cleaners then Otos are your best bet. I have all 5 gallon tanks and in 2 of them I have Otos to clean up the algae. They do an excellent job if you do not OVERFEED them on algae wafers. You do have to feed them some but not everyday if there is algae present. I have 2 Otos and a Betta and I think that is the perfect match in the 5 gallon tank. Otos are also the least affected by being chased by a frisky betta. Other fish are sometimes intimidated. They get ruffled up and then settle right down and after a while do not even let the betta bother them. Mine have even been known to swim right past the betta's nose just as if to say,
"hahaha, can't catch me"

. I do find it a little hard to feel sorry for them when they do this.
There are several methods to cycle a tank fishless and all of them are on the page of this website that deals with the
nitrogen cycle:
http://www.fishlore.com/NitrogenCycle.htm
As you scroll down the page you will find an area for "Cycling the Tank Fishless" and there are options of ways to do this. I have personally only done Option 3 but they all work with varying lengths of time and work involved. You will need a Master
test kit and not the Test Strips to do this. We here use the Aquarium Pharmaceuticals Master Test Kit more than any other, more for uniformity than because it is superior to the other Master Test Kits. The idea is that the tests need to be done with a liquid reagent and in a test tube instead of by dipping a stick as the dip sticks have been known to be very inaccurate and fail to identify the presence of unsafe levels of chemicals.
I do hope this has been helpful. Please feel free to ask any questions you may have and make any comments you need to. If we can be of help please let us know. It is a great life owning a betta. There are rewards that you will only find as you get to know your little one on a one-to-one basis. No one can tell you exactly what it will be like because every betta is a different personality and will surprise you and us with their little idiosyncrasies. Good betta hunting, the fun is going to be just beginning

.
Rose