What to look for in a LEB provider
While many, perhaps most LEB providers and offers found around the Internet are perfectly legitimate and well intentioned, even those that appear promising can disappoint by the provider going dark unexpectedly or when a provider is more frustrating to work with than their low cost can justify. The most important decision to do business with a LEB provider may be cost, but you can and should still be a discerning consumer on other grounds.
Here are some general areas to consider before committing to an offer (and likely some good additions or modifications will be forthcoming in comments to this thread). These may be equally useful bits for LEB providers to consider as well. In no particular order:
Historicity If the provider has no or a limited business history, proceed with caution. Evaluate the web site domain name history (i.e. WHOIS, archive.org). Are there well established and active social media accounts? Do their social media accounts indicate two-way conversations or are they just one-way news feeds? Do they have associated accounts on LET, WHT or other forums that indicate they've been an active provider for some time? Examine those activities if they exist.
Reputation Are there other well established users in the community who have experience with them? Are there any business registrations for the provider you can examine? Have they been independently verified by LEB or other users you trust? Self-published testimonials are usually not worth much, don't trust them. Does the provider have a reputation as a "bullet-proof" hosting provider or is otherwise associated with an excessive amount of badness? If so, it is usually best to stay clear of these providers.
Payment Options PayPal is probably the best and safest form of payment for the consumer. You should have a verified PayPal account and use that whenever possible. If things go really wrong and you have a good case, you can probably get a refund through PayPal as a last resort. I generally avoid other forms of payment, such as Bitcoin and credit cards even for established players. It depends on your level of paranoia, but keep in mind some forms of payment or document scan requirements offer you less protection or may increase the risk of some personal information exposure. Note, some providers express frustration with PayPal processing precisely for the reason consumers like it. Dealing with charge backs can be time consuming and expensive for the provider.
Language and Correctness Provider emails, web pages, advertisements, order forms, tweets and other forms of communication with basic grammatical and spelling mistakes should raise red flags. Broken links and "coming soon" pages suggest laziness. Attention to detail and clear rhetoric says a provider has made at least the minimal operational investment.
Professionalism This can come in all forms, but for example, how do provider representatives behave on forums or social media? The best providers are usually those who exhibit helpful and courteous behavior, even in the face of hostile and rude participants in forums and social media.
Salesmanship Be wary of those who skirt forum posting rules to advertise or solicit business. This is rarely the sign of a provider who is trying to build a business, but rather someone who is just trying to make a little money fast. Constant or excessive advertisement is usually a sign of desperation, rarely one of success.
Personnel Personnel operating or representing a provider should be a real person. You should not be dealing with people who only identify themselves using nick names or generic role addresses. Beware of a provider being too secretive.
Availability If you are seriously interested in a provider, but are still unsure of them, especially if they are new, it is often useful to talk to them first. Open a low priority sales ticket and inquire about their offer(s). New providers often forget to make test addresses available or may not have a yearly offer option. Ask them about it. Maybe simply send a note saying you were interested in their offer and you are considering them. If you don't get a reasonable, non-automated response within a few days to a question, then you should probably not be ordering from them.
As the consumer, you have some obligations as well. For instance, be courteous and mindful of a provider's limitations. Read the ToS. Setup automatic bill payment if you can. If you're happy with a provider, mention them as an option for others to consider if the opportunity arises. Remember that most providers are probably operating on incredibly thin margins. Less than $7 (US) a month for a well-connected Internet host with a public IP address doesn't leave much room for profit. Lastly, you should give them some idea of what they can expect from you, especially if you may be generating any traffic that could cause potential problems. Some providers are open to hosting controversial content or maybe even DDoS-magnet customers for little to no additional cost.