Your toddler’s personality is now well developed and she will be strong willed and very efficient at letting you know when she doesn’t want to do something.  She will be able to say quite a few single words, but her favourite word is “no”!   She will be able to understand simple instruction for example “give the teddy to grannie” but won’t necessarily want to do it. She thinks she is the boss in the family and that she should be centre of attention at all times. Tantrums may now be a common occurrence as she hasn’t learnt to control her emotions and so they erupt into a tantrum.   Use distraction to help her out of the tantrum and if this doesn’t work, ignore her until she comes out of it of her own accord and then praise her once she has stopped.

Your little one should be able to walk quite steadily and be able to squat down and pick things up from the floor without falling (most of the time).  She will love pull along toys and walkers that she can push.    Climbing on the furniture is fun at this age, so stay close by to help her get down.  

Her imagination is just beginning, so encourage this with toys such as dressing up clothes, tea sets etc.  She will be interested in other children and enjoy being around them, but wont yet play with them.
She will love nursery rhymes and will try and join in particularly if you do hand movements to them.  This is great for language development.   Help her learn parts of the body by pointing to them and naming them.   Looking at books together also helps with talking and is great as part of her bedtime routine.

She will want to be independent and will be able to feed herself with a spoon (this will be very messy though) but this is all part of learning, so do let her do it. She will also want to help dress herself, which can be frustrating for you as it will take far longer, but when you do have the time, encourage her to do this.  It can also be very frustrating for your little one as she wants to do more than she is able to do and it can lead to tantrums.  
The big tip for parents of an 18 month is patience, as 18 months won’t be rushed and have their own agenda for the day which often doesn’t fit in with yours.