Biblatex bibliography title fields for different entries

Question

I'd like to typeset my bibliography (which currently contains > 100 entries) and I'm strongly considering using biblatex. I'd like to try some alternatives, being one of them printing the title of an entry in bold. To that end, following the suggestion on the usage of biblatex that another user gave me, I wrote the tex code below that uses \DeclareFieldFormat{title}{\textbf{#1}}. However I only get in bold the titles for books, manuals, miscs, technical reports, but this is ignored for articles, inproceedings and unpublished work.

Which is the field from those type of entries that I need to tune in biblatex in order to print their titles in bold?

\begin{filecontents*}{biblio.bib}
@ARTICLE{ar,
         author    = {Author-ar},
         title     = {ar}}
@inproceedings{inp,
         author    = {Author-inp},
         title     = {inp}}
@unpublished{unp,
         author    = {Author-unp},
         title     = {unp}}
@techreport{tr,
         author    = {Author-tr},
         title     = {tr}}
@misc{mi,
         author    = {Author-mi},
         title     = {misc}}
@MANUAL{ma,
         author    = {Author-ma},
         title     = {manual}}
@BOOK{bo,
         author    = {Author-bo},
         title     = {book}}
\end{filecontents*}

\documentclass{article}
\usepackage[backend=bibtex8]{biblatex}
\bibliography{biblio}
\DeclareFieldFormat{title}{\textbf{#1}}
\begin{document}
Hello ~\cite{ar,inp,unp,tr,mi,ma,bo}.
\printbibliography[title={References}]
\end{document}

Generated output:

Answer 1

As soon as you set custom field formats, i.e. \DeclareFieldFormat[article]{title}{\textbf{#1}} the version without optional parameter \DeclareFieldFormat{title}{\textbf{#1}} is only applicated to entry types which have no custom format yet: @book, @inproceedings etc. – but not @article!

The starred version \DeclareFieldFormat*{title}{\textbf{#1}} will set the field format for every entry type, and overwrite them if necessary.