Romanian Loan in OCS?

Hello,
If we find a word in 2 (or more) languages (like OCS and
romanian), how do we know that this is a loan from OCS to romanian
and not a loan from Romanian to OCS. I mean what criteria we have to
follow.
And a second questions related to this :
- are there romanian loans (even not latin) in OCS? or there
are only OCS words in romanian?

I give you an example :

rom. gard , <alb. gardh, sl. gradû

in your previous discussions rom."gard" was considered as a slavic
loan in Romanian (Piotr).

However I found it in Ulfila Bible(311) as "gards" (gothic).

So
a) it is a germanic word loan by Daco-Romanians and albanians
and next used by the slavs or

b) It is a germanic word loan by slavs and next used by
Romanians and albanians

What criteria we have to use here in order to decide this?

Please give me some additional examples too.

Thanks a lot ,
marius a.