One of the Biggest advantages of a free blogging platform is its huge community and army of third party code delelopers. Writing plugin is extremely easy in WordPress and I think that causes (together with extreme popularity) the tendency of growing number of problems when using plugins. Bad coding habits of inexperienced coders multiply the mess.
These problems include cases when two plugins just wont work together, or bad coding causes php engine errors/warnings which may not be noticed until you check your error logs through cpanel. In latter case if errors/warnings generated become a substantial flaw, your hosting provider may even suspend your acc. Also, keep in mind that if php generated warnings are rare in your case, they may dramatically increase in number with grow in traffic flow. So my first tip and recommendation:
Check your Error Logs frequently, especially after you installed new software!
What to do if I get errors or if plugins just wont work on my installation? You are not alone and most likely people already experienced the same problems. The golden rule here is to read ALL comments to original plugin’s post. You can just make search for particular error words. Be careful with recommendations and posts on WordPress support forum regarding particular plugin - plugin author is rare visitor there and most help requests and error reports are answered through authour’s home page. So second tip and recommendation:
In case of errors look through all comments (this may be boring, but works) on plugin home page for your case.
In 90% cases somebody already reported your problem. But what to do if you are in those 10% unknown and unresolved cases? Write to author. If author did not resolve your case or just did not answer, but you still love that plugin? Then one more tip:
Google!!
This may sound obvious and banal but I was amazed by the fact that googling not only can help to find a user who solved this problem but also can show you a bunch of other similar plugins, which may even not listed in WordPress plugins repositories.
But what if all above steps did not work? Then just drop that plugin
Unless you are not programmer yourself and can fix the code, the headache you will experience and time spent will outperform any goods of this plugin. One of the plugins I dropped was Polyglot plugin - language switcher. Idea is good but headache was endless. And, BTW, unless you are not international corporation I do not see any sense in double/triple work writing each of your posts in several languages. Just make another blog - that’s it.
Bad plugin behavior may even cost you SE position and traffic. There is a kind of plugins whose work is not so evident compared to those which present some tangible data on your page like text or graphics. They are supposed to do some work on the background (like permalink redirect ) Authors fix bugs incrementally and some of them may work against you for a long time before you even notice it. My strong recommendation in this case - DO NOT USE These plugins unless you are 100% sure about them.
And as a final conclusion: I do not have my “Top 10 Plugins”, though I use them. On some of my blogs I do not use plugins at all (except for those which came with WordPress). Actually, WordPress gives you everything you need for blogging. Plugins just allow to add some extra bits of functionality which are not vital for the purposes of blogging. So be conservative in adding third party plugins. After struggling with some of them you may end up with understanding that they are almost useless..