Some babies don't really do set routines, so lifting that expectation can really take the pressure off as a parent.

A bedtime routine can help with establishing a pattern. You can do something similar at nap times - it can help babies to know what to expect next and a series of calming/relaxing activities (books, bathtime, walk, whatever your baby likes) can help them to unwind and get ready to sleep.

The crying and clingyness is very common at this age as separation anxiety will often set in. I know with my DS all we could do was ride it out - trying to enforce a routine or get him to sleep alone only made things worse. But it did pass.

It's all just trial and error as you figure out what works best for your baby. Personally I have found some of the advice in Pantley's No Cry Sleep Solution quite helpful.

All the best~