I think 4 & 5 are some really good points:

4. Don’t use custom fields unnecessarily – so many themes have relied on this to put more of the pressure on the author.  I think theme authors should be looking at ways to improve and simplify the workflow when possible.

5. Custom write fields! – yes, yes and yes.  I think 2010 will see many plugins and themes take advantage of custom write fields and templates.

10 More Tips To Improve Your WordPress Theme

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