Riders of Rohan - Strategy

At the start of the game, Theodred and his men are guarding the
Fords at Isen and the Harrowdale troops are nearby. They'll travel
to Isen to join Theodred, then Saruman's forces will attack.
Fight the resulting battle yourself and you should be able to win
and keep Theodred alive too.

Aragorn, Legolas and Gimli will arrive from the east into Rohan.
Soon after this, Eomer will encounter the Uruk-hai who are the
ones who captured Pippin and Merry. The Uruk-hai leader will
challenge Eomer to single combat - accept and beat him, then win
the following battle. The Hobbits escape. Get them to enter
Fangorn.  In Fangorn the Hobbits meet Treebeard, an Ent, and he
takes them to his home.

Meanwhile, Eomer meets up with Aragorn and co. Tell Eomer your
name is Strider - tell him you're hunting orcs - tell him about
rescuing your friends - claim your heritage (Eomer loans you
horses). Eomer heads back to Edoras. Orcs will attack Aragorn's
party, so go through the archery sequence or let the computer work
out the result ... just make sure Legolas wins! Enter the edge of
Fangorn - Gandalf turns up and joins the group.

By now, Treebeard, Merry and Pippin have arrived at Treebeard's
home where he pledges his support.  Eomer arrives at Edoras,
threatens Theoden's advisor, Grima, and is put into a cell.

Gandalf, Aragorn, Legolas and Gimli travel across country to
Edoras. At the gate they meet Hama who asks them to leave all
their weapons before entering. Leave all but Gandalf's staff. When
he insists, refuse to leave the staff. Explain the staff (it's to
help an old man walk ...). The party is allowed in to meet
Theoden. Grima is in attendance. When he baits Gandalf, encourage
Theoden. When Grima persists in criticising Gandalf, respond to
criticism. Then use your power against Grima. Ask Theoden to
release Eomer and after they are reunited, Theoden will mobilise
his troops and says he will fight with them. Grima will offer to
take care of things while Theoden is away. Suggest a replacement.

You suggest Eowyn takes charge, Theoden agrees and Grima is shown
in his true colours.

Once you have control of the Edoras forces, start to move them
towards Helm's Deep - avoid the mountains or you'll exhaust them!
Meanwhile the Ents will attack and destroy Isengard. Afterwards
they'll attack some of Saruman's forces who are on their way to
Helm's Deep.

Return all your troops to Helm's Deep. The Red Arrow will arrive
around this time. If all has gone as planned you should have all
the major characters alive, Theoden as King and 6,000 troops sent
to Gondor - a decisive victory!