What differenciate the good and bad hosting? what issues to consider before choosing a hosting or changing it?
Good hosting meets your needs, bad hosting doesn't.
As to what's good or bad for you depends on what you actually need from your hosting. Many people find free hosting good, many find cheap hosting good, many find hugely overpriced hosting good.
If you're hosting a personal site, then a free or cheap host will be fine for most needs, if you need high availability for an e commerce solution, then you should expect to invest a decent sum.The costs involved will generally reflect the value of your site.
Personally, I'd always go with a smaller company as you generally are more important to a small company, to a big company you can become just a user number or line entry on the sales ledger.
If cost is your only consideration, then it's very difficult to determine good from bad. Generally the cheapest hosts tend to be oversellers and often shoolboy hosts.If you're prepared to invest a bit and move off the bottom rung, then you generally get better quality hosting.
Support and uptime are the most important factors consider before choosing a host
Choosing a good host ... I always consider support,uptime and server speed depends on the site if i am running a media related site i always prefer that the server where my site is hosted able to manage requests and have good responce time. If running a small site or text based site that speed doesnt comes into play.
The hosts with good uptime record,active support,large bandwidth and affordable rates etc., could be considered as a good host.
Support and uptime are the most important factors for me. Speed of the server would be a close 2nd.