How to find a proper ontology for my classes and properties?

Hello everyone!
I have 2 questions about rdf data.

1. Suppose I started describing something in triples and I want to use a
property 'hasOwner'. I understand that it's much better to use this property
from one of the existing ontologies rather than use property from my own
namespace.
The question is: what is the easyest and the most right way to search for
this property? I know, there is Swoogle and sometimes it helps me with that.
I wonder if there is something better that fulltext search.

2. Suppose I face the dataset I never use before. What do you usually do
first to get a first impression about the dataset? At the moment I first
make some SPARQL queries to this dataset, such as:
select COUNT(?x) WHERE
{
?x a ?z .
}

than I use Marbles or Sig.ma to surf randomly over this data and finally I
come up with a opinion where I need data from the dataset or not.
Again, what do you usually do? Is there a tools or useful queries that can
help Semantic Web user in browsing data and getting useful info about
datasets?

Thank you in advance!

Yury Katkov