Tech knowledge
The one thing which should be noted is that how much tech savvy the designer is, that is how much technologically advanced the person is to make your web designing a delightful experience while at the same time bringing in new patterns of designing which will heighten the user-experience and also the navigability of the site. In order to access this you must look into the current works of the company and see whether the designers have incorporated all this in it or not. This will give you a crystal clear view of what you can expect from them, in terms of designing and all.
The creative aspect
The next thing which should be accessed is the creativity of the web designer and for this you need to ask them for sample designs for your website. Although templates will definitely be provided to you but press them for rough sample sketches to check out, whether they can make your dream vision really come out alive and this will surely be the turning point in accessing whether the hired designer from the reputed agency is competent enough to match up with your requirements. However, make sure that the designs do not get clumsy and there is adequate white space for better navigability.
Nevertheless, if you are amply satisfied with all these aspects then it is important to take a look at the charges that they are claiming for your and if it fits your budget and is of standard rates, then you are surely at the right place and it is truly a delight to get attached with the right company and in this context Ripplewerkz does deserve a mention, when you are looking for a skilled web designer.