2) Never read patents period. This is what almost all the large players do- not read them.
If you read them, you're liable for treble (3x) damages if the entity with the patent sues you and finds out you read their patent or knew of its existence. Such infringement is called "willful infringement". The default assumption WILL BE simply that you knew about the patent, understood it and stole it deliberately.
Never read them, never browse them, never click on a link from some of the patent spam websites out there who push patent results on searchers. Their business model, if you can call it that, is to record the IP address of everyone who reads any patent then sell that information to patent holders for the purposes of securing treble damages in lawsuits.
3) consider not selling software in the following jurisdictions: USA, Australia, Japan, South Korea. Those are the big countries who are completely promiscuous with respect to patenting virtually any anything; essentially they permit the patenting of ideas, although they will tell you that's not true.
You can still make a fine living selling into the EU New Zealand and other more enlightened and business friendly countries and not risk being sued out of existence.
Finally, people will tell you false things to convince you you'll be OK selling in the US. Don't listen to them. Here are some of the things they'll say:
* No one will sue you until you have enough money to make it worth their while, at which you won't care because you'll have a lot of money.
This is false. Small companies who make no money and whom you've never heard of get sued every day by slightly larger companies. Why? For a variety of reasons.
One is because if it can be shown in court that the patent-holder did NOT pursue patent enforcement, their patent can be rendered unenforceable. Companies have a statutory obligation to pursue known infringers or risk losing their IP rights.
Another reason is to kill off free alternatives to their product offering. To take one current instance, this is happening now to a flight planning software named Navmonster and a few others by a competitor. Navmonster doesn't make money; it didn't save them.
Another reason is to kill off a slightly smaller competitor or nip a new entrant in the bud,
Remember, it takes many hundreds of thousands of dollars to defend yourself against a lawsuit. If you get served, you're done. They know this and leverage it.
No one will notice you.
Lionel trains noticed the home hobbyist who was using software to control Lionel trains. They shut him down. Don't kid yourself. Is it worth risking everything you have on a hope that you fly under the radar when flying under the radar also means not becoming really successful?
Only large players sue each other.
This is simply false. There are many many counter examples but no one knows how many companies throw in the towel upon being served with infringement claims. No one tracks this number since it only amounts to a letter from a lawyer to a company in most cases and no court records are generated. If you look for counter examples, you'll find them. Lots of them on an ongoing basis.
Patent trolls only go after deep pockets.
This is really the same argument as the above, and it's not true. It's based on the idea that patent trolls all act in the same way, essentially some scenario in which they sue seeking huge compensatory damages against rich companies. This describes ONE reason someone would sue and ONE kind of plaintiff. In no way does it describe the motivations of litigants or the variety of legal activity that results in a company being put out of business by a software patent lawsuit.
Take this seriously. The best way to not have everything you've worked for taken away from you is to not release it in jurisdictions that could happen in in the first place. Markets that are not going to permit that to be done to you are big enough for an ISV.
Incidentally, it's interesting to reflect on where the term ISV came from. It came from the press's wish to distinguish Independent Software Vendors from Microsoft. Or in other words, the software market is so dominated by Microsoft that all companies are divided into M$ and ISVs.
It's also interesting to note that M$ pushes software patents as a strategic device to deny entry by small players who can neither afford to acquire nor defend them.
Of course they're aided in this by all companies and individuals who are positioned to benefit from the enormous barrier to entry such a system creates against small companies.
Essentially software patents are a way for largish companies to make sure no smaller company can compete with them on value to the consumer. They are also a way for IP attorneys to inject themselves into the software revenue stream where they would naturally have only a limited role. In this they are completely parasitic, contributing nothing of productive value. Software patents are best thought of as a tax upon software by IP lawyers who have developed a pay-to-play scheme against software developers.
Best of luck. I agree you should consult a lawyer. Perhaps one the best questions you might ask is how to get set up to do business in the EU, New Zealand, India, Canada and anywhere else where you can produce software, sell it and rise and fall by the goodness of your efforts and the value you deliver rather than live like a serf in the US: only at the pleasure of the King.